Effectiveness of a Novel Home-Based Testing Device for the Detection of Rupture of Membranes Jacob Bornstein, M.D.,1,2 Gonen Ohel, M.D.,2,3 Yoram Sorokin, M.D.,4 Kathleen Z. Reape, M.D.,5 Oleg Shnaider, M.D.,1 Hadar Kessary-Shoham, Ph.D.,6 and Ella Ophir, M.D.1,2
ABSTRACT
We evaluated the ability of a testing panty liner (TPL) embedded with a pH/ammonia indicator polymer to differentiate amniotic fluid leakage from urine. A multicenter, open-label study in which 339 pregnant women (age 18 to 45 years, minimum 16 weeks’ gestation, presenting with unexplained vaginal wetness) were enrolled. The TPL was worn and the results read by the subject and a health care provider (HCP) who was blinded to the subject’s reading. Results were compared with the standard clinical diagnosis, as determined by direct visualization of vaginal pooling, crystallization (ferning), and nitrazine tests, performed by a second blinded HCP. Subject experience with the test was assessed with a brief questionnaire. The TPL accurately detected 154 of the 161 subjects found to have amniotic fluid leakage by the standard diagnosis; thus, the sensitivity of the TPL was 95.65%. The specificity was 84.46% (% true negative readings), as the TPL demonstrated a negative result for 125 of the 148 subjects whose clinical diagnosis was negative for amniotic fluid leakage. The overall agreement between the TPL readings of the clinician and that of the subject was 97.40%. The TPL is a reliable test to determine the presence of amniotic fluid leakage. KEYWORDS: Amniotic fluid leakage, testing panty liner
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eakage of amniotic fluid during pregnancy may occur as a result of normal physiological processes when in labor, abnormally when it is preterm, or following amniocentesis.1,2 The risk of maternal intrauterine infection and possible vertical transmission of group B streptococci during labor or delivery increases with the duration of membrane rupture prior to delivery.1–3 Fetal risks with leakage of amniotic fluid include umbilical cord compression or prolapse and ascending infection as
well as other factors related to gestational age and fetal status at delivery.2 Detection may be especially difficult if the leakage is slow or intermittent. Digital cervical examination may increase the risk of infection and should be avoided in preterm premature rupture of membranes.1 Other diagnostic methods include visualization of the posterior fornix of the vagina for pooling of amniotic fluid, use of nitrazine/pH paper to test vaginal secretions, microscopy to identify crystallization
1 Western Galilee Hospital, Nahariya, Israel; 2Rappaport Faculty of Medicine, Hatechnion University, Haifa, Israel; 3Bnai-Zion Medical Center, Haifa, Israel; 4Wayne State University, Hutzel Women’s Hospital, Detroit, Michigan; 5Clinical Operations and Medical Affairs Duramed Research Inc., Bala Cynwyd, Pennsylvania; 6CommonSense, Caesarea Industrial Park, Israel. Address for correspondence and reprint requests: Kathleen Z.
Reape, M.D., Duramed Research Inc., One Belmont Avenue, Suite 1100, Bala Cynwyd, PA 19004 (e-mail:
[email protected]). Am J Perinatol 2009;26:45–50. Copyright # 2009 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: +1 (212) 584-4662. Accepted: June 18, 2008. Published online: October 31, 2008. DOI 10.1055/s-0028-1095183. ISSN 0735-1631.
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(ferning) of amniotic fluid, and immunoassay for the presence of placental a microglobulin-1 used alone or in combination.1,4,5 Urinary incontinence and other sources of vaginal discharge from vaginal infections such as bacterial vaginosis and trichomonas vaginitis may confound the interpretation of results and make the presence of amniotic fluid leakage difficult to detect. An ideal diagnostic aid for the detection of amniotic fluid leak would be noninvasive, inexpensive, easy to use, easy to read, and available for use at home to detect intermittent fluid leakage over a period of time. In addition, it would provide high sensitivity, high specificity, and could differentiate amniotic fluid from other sources of vaginal discharge or urinary incontinence. In a feasibility study to assess the effectiveness of a panty liner embedded with an indicator strip to detect amniotic fluid, investigators concluded that the panty liner (AL-SENSE panty liner; subsequently renamed AmniScreenTM) was a highly sensitive method to determine amniotic fluid leakage.4 The testing panty liner (TPL) was further evaluated in a larger, multicenter, open-label, prospective clinical trial to determine its ability to detect possible leakage of amniotic fluid in pregnant women with unexplained vaginal wetness.
MATERIALS AND METHODS Pregnant women (minimum 16 weeks’ gestational age) between the ages of 18 and 45 years old presenting to the labor and delivery triage area at each of the investigative sites and reporting a feeling of vaginal wetness (undetermined if due to amniotic fluid leakage or urine) were eligible to participate in the study. Women with gross rupture of membranes were excluded; women in active labor were not excluded. A total of 339 subjects were enrolled between May 1, 2006 and November 22, 2006 in two centers in Israel (Western Galilee Hospital, Nahariya and Bnai-Zion Medical Center, Haifa) and one center in the United States (Wayne State University/Hutzel Women’s Hospital, Detroit, MI). Informed consent was obtained from all participants. The institutional review board for each hospital approved the study protocol. The AmniScreenTM (Common Sense, Ltd., Hesarea, Israel) TPL is comprised of a regular panty liner with an embedded test strip coated with a proprietary polymer containing a colorimetric pH indicator, which immediately changes color from yellow to bluegreen upon contact with fluids, such as amniotic fluid, with a high pH ( 5.2 units). Unlike nitrazine paper, the TPL distinguishes between amniotic fluid and urine by use of a polymer matrix that has a specific composition of ingredients that reverses the color change back to yellow by reacting to concentrations of ammonia exceeding 6 mM, such as urine, within 30 minutes (of drying time). The pH indicator is chemically bonded to a
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polymer and absorbed on polyester mesh that is inserted under two upper unidirectional absorption layers. There is no direct physical contact between the woman’s body and chemicals or the diagnostic component of the TPL. The TPL underwent tests to evaluate cytotoxicity, skin irritation, and sensitization and complies with the U.S. Pharmacopoeia Guidelines.4,6,7 Subjects were excluded from participation in the study if any of the following criteria were present: intermittent vaginal bleeding during the second or third trimesters, sexual intercourse within the past 12 hours, unable or unwilling to cooperate with study procedures, prior use of the TPL, diagnosis of bacterial vaginosis or trichomonal vaginal infection within the past 3 days, use of vaginal products or antibiotic treatments that reduce lactobacillus population, use of medications such as tamoxifen that reduce estrogen levels or antihistamines that dry mucous membranes, or consumption of alkalizing foods (such as broccoli, beets, cabbage) that could elevate vaginal pH levels. A healthcare provider (HCP) explained the proper use and handling of the TPL as well as how to read the results. Subjects remained in the hospital during the study assessment period. Subjects received a single TPL to wear for up to 12 hours or until vaginal wetness was noticed, at which point the TPL was removed and placed in a drying tray for 30 minutes. The subject then observed the TPL and recorded any color change. Independently, an HCP blinded to the subject’s result record also observed the TPL and noted any color change. After the TPL was used and read by first the subject and then by the first blinded HCP, evaluation for amniotic fluid leakage using standard diagnostic methods was performed by a second HCP who was blinded to the TPL results. The standard clinical diagnosis was determined by performing a vaginal pooling test, ferning test, and pH test with nitrazine paper. A positive standard clinical diagnosis was defined as either a positive pooling test or positive results in both the ferning and pH/nitrazine tests. The results of the standard clinical diagnosis were compared with the subject’s reading of the TPL results and used to calculate the sensitivity and specificity of the TPL. When the results of the subject reading of the TPL test were in agreement with the standard clinical diagnosis results (either positive or negative), no additional testing was performed. However, in cases of a discrepancy between the TPL test and the standard clinical diagnosis results, the procedures were as follows: If the TPL was positive and standard clinical diagnosis was negative, the subject was evaluated to rule out the possibility of a vaginal infection (bacterial vaginosis or trichomonas vaginitis), and a second clinical assessment (pooling, ferning, pH/nitrazine tests) was repeated within 48 hours to determine a final clinical diagnosis. The presence of vaginal bleeding, bacterial vaginosis,
HOME-BASED TESTING DEVICE FOR DETECTION OF RUPTURE OF MEMBRANES/BORNSTEIN ET AL
or trichomonal discharge was likely to lead to a falsepositive test (i.e., stain the TPL blue-green) and the stain would not reverse because, unlike urine, these fluids do not contain a high ammonia concentration. The result was deemed a false-positive if the TPL was positive, the standard clinical diagnosis was negative, and the subject had a positive diagnosis of bacterial vaginosis or trichomonas vaginitis. If the TPL was negative and clinical assessment results were positive, no further testing was needed. Any necessary treatment was based on the results of the standard clinical diagnosis and not on the results of the TPL test. The final clinical diagnosis was defined as positive when the standard clinical diagnosis was positive (positive pooling test or positive results in both the ferning and pH tests) either initially or when testing was repeated within 48 hours. Participants completed a short questionnaire evaluating their experience with the TPL and their understanding of the results. The first three questions asked the subjects to rate the TPL on a scale of 1 to 5 regarding their understanding of how to read the results and the comfort of the TPL. Two questions evaluated subject comprehension of the results.
Statistical Methods Although not directly comparative, this study was designed to demonstrate that the TPL was not inferior to the AmnioTestTM (nitrazine swab; Pro-Lab Diagnostics, Richmond Hill, ON, Canada) in its ability to detect possible leakage of amniotic fluid in pregnant women with unexplained vaginal wetness. The reported sensitivity and specificity values for the nitrazine swab are 91% and 73%, respectively.8–10 Thus, the goal of the study was to show that the TPL would demonstrate 91% sensitivity and 73% specificity In a small pilot study, the TPL demonstrated a sensitivity of 100% (for sample size estimation a conservative estimate of 97% was used for sensitivity) and a specificity of 84%.4 A sample size for the current study was estimated for two separate noninferiority hypotheses, which are meant to be evaluated with one-sided exact binomial tests, assuming that sensitivity will be 97% to reject a null hypothesis that sensitivity is less than 91% with over 80% power; 100 positive women are required, and, assuming that specificity will be 84% to reject a null hypothesis that specificity is less than 73% with over 80% power, 90 negative women are required (PROC POWER with SAS software, version 9.1; SAS Institute, Cary, NC). In addition, based on an expected prevalence of amniotic fluid leakage (65%) along with a subject dropout rate of 20%, it was determined that 323 women would be required for the study. Subjects with valid results from both the TPL and all three components of the standard clinical diagnosis were included in the per-protocol analysis set. These
subjects served as the primary analysis cohort for inferences regarding effectiveness; however, a single analysis (TPL compared with final clinical diagnosis) using any evaluable data from the intent-to-treat cohort was conducted. The secondary endpoints compared the clinician’s reading to the final clinical diagnosis and evaluated the subject’s comfort level with the test. The primary analysis, as defined in the protocol, compared the agreement between the subject reading of the TPL results and that of the final clinical diagnosis regarding the presence or absence of amniotic fluid. The primary endpoints were evaluated by constructing a 2 2 table comparing the subject reading of TPL results to the results of the clinical diagnosis. The sensitivity (% true positive) and specificity (% true negative) of the TPL were calculated from the table. Subject results were also compared with the standard clinical diagnosis, a conservative approach that is more representative of clinical practice, as the diagnostic tests (pooling, ferning, pH/nitrazine) are generally not repeated within 48 hours after a single episode of unexplained vaginal wetness. The percentages of subjects assigning a positive score (rating of 4 or 5 out of 5) in the subject questionnaire were calculated and are presented descriptively.
RESULTS Of the 339 women who were enrolled in the study, 10 subjects were found to have violated the protocol exclusion criteria and were discontinued (six had had sex within the last 12 hours, one had used a vaginal product that could affect pH, one had bacterial vaginosis, one had intermittent bleeding between the second and third trimesters, and one did not complete her results form). An additional 20 subjects were removed from the outcome analysis as they did not complete one or more of the three required tests (pooling, ferning, nitrazine/pH) needed to determine a final clinical diagnosis. There was no statistically significant difference in the exclusion rates between the three centers (p ¼ 0.33; x2 test). Demographic data and baseline medical information were summarized and are presented for all 339 subjects who signed informed consent between May 1, 2006 and November 22, 2006 (Table 1). Effectiveness data are presented for the per-protocol cohort (n ¼ 309). Although distributions in several demographic parameters between the investigational sites were statistically significant, none were deemed clinically relevant (Table 1). The average gestational age of the participants in the study was 37.2 weeks (range 17 to 42 weeks’ gestation). This was the first pregnancy for 37% of the women enrolled. The majority of women reported that they had never had a spontaneous abortion (63%), elective/therapeutic abortion (77%), or prior premature delivery (93%). Approximately 7% were taking antibiotics
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Table 1 Demographics Bnai Zion (n ¼ 110)
Detroit (n ¼ 50)
Western Galilee (n ¼ 179)
Overall (n ¼ 339)
p Value
Age, y (mean SD)
29.9 4.9
25.4 5.5
26.7 5.7
27.5 5.7
< 0.0001
Country of origin
—
—
—
—
< 0.0001
Israel or U.S. (i.e., local)
77 (70.0)
48 (96.0)
161 (89.9)
286 (84.4)
—
Other
33 (30.0)
2 (4.0)
18 (10.1)
53 (15.6)
—
1 2
33 (30.0) 30 (27.3)
13 (26.0) 12 (24.0)
81 (45.3) 30 (16.8)
127 (37.5) 72 (21.2)
— —
3þ
47 (42.7)
25 (50.0)
68 (38.0)
140 (41.3)
—
Prior pregnancies, n (%)
at the time of enrollment. Per the study protocol, 4% had a vaginal smear to rule out bacterial vaginosis or trichomonas vaginitis if the TPL result was positive and the standard clinical diagnosis was negative. The primary outcome analyses were conducted on those subjects who had TPL test results and had completed all three tests required for the standard and final clinical diagnoses (n ¼ 309); comparisons were made between the subject reading of the TPL results and the results of both the standard and final clinical diagnoses. In most cases (286/309, 92.6%), there was agreement between the TPL results and the standard clinical diagnosis, so it was not necessary to repeat the clinical diagnosis within 48 hours (per the protocol, if there was agreement, the standard clinical diagnosis served as the final clinical diagnosis). Of the 23 cases where there was a mismatch between the TPL results and the standard clinical diagnosis, four were diagnosed as positive at the final clinical diagnosis and 19 were considered false-positives. Of the 309 subjects in the per-protocol analysis, 161 were diagnosed with amniotic fluid leakage by the standard clinical diagnosis and 148 were negative. The sensitivity (% true positive) of the TPL based on the subject’s reading and confirmed by standard clinical diagnosis was 95.65% (154/161). The specificity (% true negative) of the TPL of the subject’s reading was 84.46% (125/148). The positive predictive value, or the probability that the subject with a positive test was a true positive and had amniotic fluid leakage, was 87.0%. The negative predictive value, or the probability that a subject with a negative result did not have amniotic fluid leakage, was 94.7%. As would be expected, relating the subject reading of the TPL to the final rather than the standard clinical diagnosis resulted in very similar levels of sensitivity (95.76%, 158/165) and specificity (86.81%, 125/144), because the standard clinical diagnosis served as the final clinical diagnosis in more than 90% of the subjects. The null hypothesis for sensitivity (that sensitivity is less than 91%) was rejected, as the p value for the one-sided binomial test was 0.02, with the conclusion that the sensitivity of the subject reading of the TPL (compared
with the final clinical diagnosis) was significantly higher than 91%. The null hypothesis for specificity (that specificity is less than 73%) was rejected, as the p value for the one-sided binomial test was less than 0.0001, with the conclusion that the specificity of the subject reading of the TPL (compared with the final clinical diagnosis) was significantly higher than 73%. The results of the single primary outcome analysis conducted on the intentto-treat cohort, which included all subjects with any evaluable data (but not all three required diagnostic tests—pooling, ferning, nitrazine/pH [n ¼ 322]), and compared the subject reading of the TPL to the final clinical diagnosis, were also similar (sensitivity ¼ 95.40%, specificity ¼ 85.81%), supporting the effectiveness findings from the cohort of subjects completing all three required tests. The Kappa statistic between the subject readings and the final clinical diagnosis was 0.83 (95% confidence interval [0.768, 0.892]), which indicates excellent overall agreement between the subject reading of the color change of the panty liner and the final clinical diagnosis.11 The clinician assessments of the TPL results were compared with the final clinical diagnosis. The sensitivity of the TPL based on the clinician reading compared with the final clinical diagnosis was 95.78%, and the specificity was 88.11%. The Kappa statistic between the clinician’s reading and the final clinical diagnosis was 0.84 (95% confidence interval [0.7823, 0.9029]), which indicates very high agreement between the two. The overall agreement between the TPL reading by the clinician and by the subject was 97.40%, with a 95% exact binomial confidence interval of [94.95%, 98.87%]. From the lower confidence limit, it can be concluded that the agreement level was at least 90%. The Kappa statistic between the clinician reading and subject reading of the TPL results was 0.947 (95% confidence interval [0.911, 0.983]), which indicates very high agreement. The participants were requested to complete a brief questionnaire to evaluate their experience with the TPL and to assess their understanding of the results of the color change on the strip. Almost 100% responded that the blue-green stain on the strip was clear (73/309)
HOME-BASED TESTING DEVICE FOR DETECTION OF RUPTURE OF MEMBRANES/BORNSTEIN ET AL
or very clear (234/309) to distinguish and that the results were clear (112/309) or very clear (193/309). Two-thirds of the participants responded that they were comfortable or felt no discomfort (206/309) when using the TPL. Two women reported that they felt very uncomfortable using the TPL, although they noted that this was similar to what they felt when using any regular panty liner. The remaining respondents were indifferent (101/309). Approximately half of the women stated that they understood that the cause of wetness was due to amniotic fluid leakage. The last question assessed the subject’s interpretation of the results if the color change faded and disappeared. A large proportion of the women did not respond to this question, and many others were unsure of how to interpret the TPL findings. There were no statistically significant differences in sensitivity between the study centers. However, a statistically significant difference (p ¼ 0.02) was observed in specificity between study sites due to a lower value at the Detroit site (69.23%) compared with the centers in Bnai Zion (92.11%) and Western Galilee (90%). This difference in specificity between sites may be explained by the rate of false-positive results due to vaginal infections. Of the 15 women at the Detroit site who tested negative for amniotic fluid leakage by standard clinical diagnosis, 23% (n ¼ 6) were found to have bacterial vaginosis or trichomonas vaginitis. There were no adverse events related to the use of the TPL reported during the course of this study.
DISCUSSION Prompt, accurate diagnosis of amniotic fluid leakage may reduce trips to the hospital and patient anxiety. Often, an amniotic leak may be slow or intermittent, so a diagnostic aid that can be self-applied at home, collects amniotic fluid continuously, and does not require vaginal exams could potentially be helpful as an adjunct to clinical exams in reducing hospitalization for observation or evaluation of suspected amniotic fluid leakage. The results of this study indicate that the TPL was a sensitive tool for excluding ruptured membranes and for differentiating amniotic fluid leaks from other sources of vaginal discharge or urinary incontinence. The TPL can continuously collect fluid over time, compared with other diagnostic tests that evaluate fluid leakage at a single point in time with the woman in a supine position. In this study, the specificity at the investigative sites in Israel was 90%. The specificity at the study site in the United States was significantly lower, which could be attributed to the number of women with previously undiagnosed bacterial vaginosis or trichomonas vaginitis and false-positive results due to these vaginal infections. The pH of vaginal discharge secondary to bacterial vaginosis or trichomoniasis may exceed 5.0, leading to a color change from yellow to green on the TPL
indicator strip and a false-positive result.12,13 In the United States, the prevalence of bacterial vaginosis varies from 10 to 40%.14–16 Moreover, bacterial vaginosis prevalence varies with age, race or ethnicity, education, and economic status.16 It should be noted that demographic data collected for this study did not include race. Although the prevalence of bacterial vaginosis and trichomonas vaginitis can introduce variability in the specificity of the TPL, the detection of vaginal infection in pregnancy due to false-positive results can be clinically valuable information. In this study, the TPL correctly detected 154 of 161 cases of amniotic fluid leak; the seven cases that were missed could have been due to a large volume of urine leakage that covered all of the area stained by the amniotic fluid. The standard clinical diagnosis in the study missed four cases of amniotic fluid leak, probably due to intermittent amniotic fluid leakage. Therefore, under the conditions of the study in the hospital setting, the sensitivity of the TPL was similar to that of the standard clinical diagnosis. It was not feasible to conduct the study in the subjects’ homes; this study was conducted in a hospital-based labor and delivery triage setting because that is where women with unexplained vaginal wetness would be most likely to present and it is where the clinical diagnostic tests could be reliably performed in a standardized fashion. However, the methods utilized in the study were designed to replicate the same steps that a woman would go through if using the TPL at home. Overall, there was a very high level of agreement in comparing the reading of the results between the subjects and the clinicians, which suggests that the TPL is suitable for use as a home test. The responses on the subject questionnaire indicate that the majority of subjects thought the TPL was comfortable to use and the results were easy to read. The answers to the questions as well as the subjects’ actual reading of the test demonstrate that women can successfully interpret the results. In conclusion, this study confirms the findings of the previous feasibility study and demonstrates that the TPL is a highly sensitive, nonintrusive method to detect the presence of amniotic fluid. False-positive results may occur in women with bacterial vaginosis or trichomonas vaginitis experiencing vaginal discharge; however, that information may be useful for the management of the pregnancy. The TPL is suitable for use in the outpatient setting, as the results are easy for the subject to read and understand.
ACKNOWLEDGMENTS
The study was supported by CommonSense, Caesarea Industrial Park, Israel. Duramed Research (Bala Cynwyd, PA) provided support for editorial services associated with the development of the manuscript. The data contained in
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this manuscript was accepted in abstract form to the American College of Obstetricians and Gynecologists Annual Meeting 2008.
REFERENCES 1. American College of Obstetricians and Gynecologists (ACOG) Practice Bulletin. ACOG Committee on Practice Bulletin No. 80: premature rupture of membranes. Clinical management guidelines for obstetrician-gynecologists. Obstet Gynecol 2007;109:1007–1019 2. Mercer BM. Preterm premature rupture of the membranes: current approaches to evaluation and management. Obstet Gynecol Clin North Am 2005;32:411–428 3. American College of Obstetricians and Gynecologists. ACOG Committee Opinion: number 279, December 2002. Prevention of early-onset group B streptococcal disease in newborns. Obstet Gynecol 2002;100:1405–1412 4. Bornstein J, Geva A, Solt I, et al. Nonintrusive diagnosis of premature ruptured amniotic membranes using a novel polymer. Am J Perinatol 2006;23:351–354 5. Cousins LM, Smok DP, Lovett SM, Poetler DM. AmniSure placental alpha microglobulin-1 rapid immunoassay versus standard diagnostic methods for detection of rupture of membranes. Am J Perinatol 2005;22:317–320 6. Section 5.510(k) Summary. AmniScreenTM Home Detection Liner Kit. Available at: http://www.fda.gov/cdrh/pdf7/ K071100.pdf. Accessed June 4, 2008 7. AmniScreenTM Home Detection Liner. Prescribing Information. Duramed Pharmaceuticals, Inc. Available at: http:// www.amniscreen.com/hcp/about_amniscreen.aspx. Accessed June 4, 2008 8. Watanabe T, Minakami H, Itoi H, Sato I, Sakata Y, Tamada T. Evaluation of latex agglutination test for alpha-fetoprotein
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in diagnosing rupture of fetal membranes. Gynecol Obstet Invest 1995;39:15–18 Garite TJ, Gocke SE. Diagnosis of preterm rupture of membranes: is testing for alpha-fetoprotein better than Ferning or Nitrazine? Am J Perinatol 1990;7:276– 278 Kishida T, Hirao A, Matsuura T, et al. Diagnosis of premature rupture of membranes with an improved alphafetoprotein monoclonal antibody kit. Clin Chem 1995;41: 1500–1503 Fleiss JL, Levin B, Cho Paik M. Chapter 18: The measure of interrater agreement. In: Statistical Methods for Rates and Proportions, 3rd Ed. Hoboken, NJ: John Wiley and Sons; 2003:598–605 Riordan T, Macaulay ME, James JM, et al. A prospective study of genital infections in a family-planning clinic: microbiological findings and their association with vaginal symptoms. Epidemiol Infect 1990;104:47–53 Eschenbach DA, Hillier S, Critchlow C, Stevens C, DeRouen T, Holmes KK. Diagnosis and clinical manifestations of bacterial vaginosis. Am J Obstet Gynecol 1988;158: 819–828 Hillier SL, Nugent RP, Eschenbach DA, et al. Association between bacterial vaginosis and preterm delivery of a low-birth-weight infant. The Vaginal Infections and Prematurity Study Group. N Engl J Med 1995;333: 1737–1742 Koumans EH, Markowitz LE, Hogan V. CDC BV Working Group, Indications for therapy and treatment recommendations for bacterial vaginosis in nonpregnant and pregnant women: a synthesis of data. Clin Infect Dis 2002;35(suppl 2): S152–S172 Allsworth JE, Peipert JF. Prevalence of bacterial vaginosis: 2001–2004 National Health and Nutrition Examination Survey data. Obstet Gynecol 2007;109:114–120
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International Journal of Clinical Medicine, 2011, 2, 307-309 doi:10.4236/ijcm.2011.23052 Published Online July 2011 (http://www.SciRP.org/journal/ijcm)
The AL-SENSE Test is Reliable for Detection of Second Trimester Amniotic Fluid Marwan Odeh1,2, Ella Ophir1,2, Hadar Kesari-Shoham3, Olga Maximovsky1, Jacob Bornstein1,2 1
Department of Obstetrics and Gynecology, Western Galilee Hospital, Nahariya, Israel; 2Rappaport Faculty of Medicine, Technion, Haifa, Israel; 3Commonsense, Caesarea, Israel. Email:
[email protected] Received December 13th, 2010; revised April 10th, 2011; accepted May 5th, 2011.
ABSTRACT Objective: To validate the reliability and stability of the AL-SENSE panty-liner for detection of amniotic fluid in the second trimester. Study design: Amniotic fluid drawn during amniocentesis between 16 to 23 weeks of gestation was used for the study.100 µl and 400 µl of amniotic fluid, were dripped onto two panty liners, respectively. After 5 minutes the indicator strip was removed from the AL-SENSE, dried and examined. The color was recorded at time 0 and 5 minutes, and then every 10 minutes for the first 30 minutes, then at 1, 2, 6 and 12 hours. Results: 50 women were enrolled and 49 completed the study. 100% of both volume samples changed color from yellow to blue during the first 5 minutes and remained stable after twelve hours of follow-up. In the 100 μl subgroup, seven of the 49 samples (14.3%) had a delayed color change and in the 400 μl subgroup one of 49 (2.04%) had a delay in change of color. Conclusions: Amniotic fluid drawn during amniocentesis at weeks 16 - 23 of gestation have a positive, stable staining effect on the AL-SENSE panty liner. Hence, AL-SENSE may be reliable for detection of amniotic fluid leakage during the second trimester. Keywords: Panty Liner, Amniocentesis, Second Trimester, Premature Rupture of Membranes
1. Introduction Recently, a diagnostic panty-liner kit—“AL-SENSE”® (Commonsense, Caesarea, Israel) was developed to detect amniotic fluid leak. Its mechanism of action is described elsewhere [1]. The panty-liner has several advantages. Firstly, it is worn by the women for some hours, so it reflects a relatively lengthy time period and not a single point in time, which increases its sensitivity in detecting minor amniotic fluid leakage. In addition, it contains a unique polymer that is capable of differentiating amniotic fluid from urine. In previous third trimester clinical studies [1,2], the AL-SENSE panty-liner test was documented as a sensitive tool for diagnosing premature rupture of the membranes (PROM) and differentiating amniotic fluid leaks from urinary incontinence. One study showed 100% negative and 87.1% positive predictive values, with a sensitivity of 100% and specificity of 75%. Another study showed 94.7% negative and 87% positive predictive value with a sensitivity of 96% and specificity of 84%. The panty-liner was compared to a series of conventional tests such as speculum examination, nitrazine Copyright © 2011 SciRes.
test, microscopic evaluation for ferning and ultrasound determination of intra-uterine amniotic volume [2]. These results were confirmed by another study [3] comparing the panty-liner test to speculum examination for detection of ruptured membranes; it found 98% sensitivity and 65% specificity. Those studies enrolled women mostly at the third trimester. However, since amniotic fluid leakage during the second trimester has even more serious complications and poor outcomes than during the third trimester, the present study was undertaken to establish the AL-SENSE reliability in the second trimester and to validate the stability time of the positive color of AL-SENSE stains even after exposure to very small of early second trimester amniotic fluid. The amniotic fluid was drawn at genetic amniocentesis between 18 and 23 weeks of gestation.
2. Materials and Methods The study was approved by the local Institutional Review Board (Helsinki committee) and written informed consent was obtained from each patient prior to enrollment. IJCM
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The AL-SENSE Test is Reliable for Detection of Second Trimester Amniotic Fluid
The AL-SENSE comprises a regular panty-liner and is worn as any other hygienic panty-liner. Inside the panty-liner the AL-SENSE contains one strip of (color) indicator that is sensitive to pH levels. The indicator strip reacts immediately to any contact with amniotic fluid or other vaginal discharge of pH 5.2 or greater. Observing a change in the color of the pH indicator indicates either a leak of amniotic fluid or a urine leak. The indicators were placed in a drying box and observed to determine the stability of the stain. During amniocentesis performed for medical reasons (primarily age over 35 years), between 18 and 23 weeks of gestation, 0.5 ml of amniotic fluid, of the 30 ml usually drawn, were used for this study. Two volumes of amniotic fluid, 100 µl and 400 µl, were dripped onto two AL-SENSE panty liners numbered 1 and 2, respectively. After five minutes the indicator strip was removed from the AL-SENSE and the strips were placed in the drying units. The color status was recorded from both panty-liners immediately, after 5 and 10 minutes, and then every 10 minutes for the first 30 minutes and within 1, 2, 6 and 12 hours after removing the indicator strip and placing it in the drying unit.
3. Statistical Analysis Statistical analyses were performed using SAS® v9.1 (SAS Institute, Cary N.C., USA). Descriptive statistics are presented in a table. Study results are presented as counts or percentages together with a 95% exact binomial confidence interval when relevant.
4. Results Fifty (50) women were enrolled in the study; 49 (98%) completed it. One patient was excluded due to a protocol deviation. The distribution of gestational age is presented in Table 1; most women were in their 18th -19th week of gestation. One hundred percent of samples in both volumes (95% CI: (92.75% - 100%)) changed color from yellow to blue within five minutes and the color remained stable Table 1. Distribution of gestational age by weeks. Gestational Week 16 17 18 19 20 21 22 23 Total
Copyright © 2011 SciRes.
N 1 3 16 21 5 1 1 1 49
% 2.0 6.1 32.7 42.9 10.2 2.0 2.0 2.0 100.0
throughout the twelve hour follow-up period. Initial indicator color change did not occur at time 0 for all the samples. In the 100 μl subgroup 7 of the 49 samples, or 14.3% (95% CI: (5.94% - 27.24%)), had a delayed color change and in the 400 μl subgroup 1 of 49, i.e. 2.04% (95% CI: (0.05% - 10.85%)), showed a delay in color change.
5. Discussion In the present study the AL-Sense panty-liner was found to be very sensitive and changed its color in response to a very small amount of second trimester amniotic fluid obtained at amniocentesis. The color change was stable for 12 hours, the time determined in advance as the completion of the study. So far, the validity of the AL-Sense panty liner has been proven in clinical studies in diagnosing premature rupture of membranes in the third trimester [1-3]. However, the effectiveness of this test had not been tested in second trimester pregnancies. This study utilized amniotic fluid obtained during amniocentesis. Therefore, the effectiveness of this test should be verified in a clinical setting, as the color of the panty-liner may change in reaction to vaginal secretions when infections that cause elevated pH are present (as stated by the manufacturer). Nevertheless, Mulhair et al. [3] found that women with positive high vaginal swabs did not differ significantly and nine women with positive high vaginal swab had a negative test (no color change). The high pH level of amniotic fluid (7.42) even at very early stages of pregnancy [4], the ability of the panty-liner to detect it, even in very small amounts (100 µl), and the long term stability of the stain makes it a very useful tool in diagnosing cases with premature rupture of the membranes in the second trimester. This period of pregnancy may be associated with significant management dilemmas due to the high percentage of fetal, neonatal and maternal complications with PROM at that time [5-7]. The high sensitivity of this test in clinical studies (100%) makes it very helpful in reassuring patients that membranes have not ruptured. A drawback of this test is its low specificity; hence, when the test is positive the diagnosis should be verified by other means. However, in this study, as we dripped amniotic fluid directly on the panty-liner and there was no contact with vaginal discharge or other fluide, we did not include a positive/negative control. Another possible use of this test is in patients experiencing post-amniocentesis fluid leakage. Since most of these cases may be followed expectantly [8,9] the test can be used to indicate cessation of amniotic fluid leakage (when a positive test become negative). In conclusion, the panty-liner is effective in the second trimester of pregnancy and can be used at that time IJCM
The AL-SENSE Test is Reliable for Detection of Second Trimester Amniotic Fluid
to detect small amounts of amniotic fluid leakage, and to exclude its presence if the leakage consists of urine. It is very sensitive and detects small amounts of amniotic fluid drawn during amniocentesis. As the present study has been conducted in vitro, the efficacy of AL-Sense should be further verified in clinical studies of women with fluid leakage during the second trimester, in the same way as it has been tested in women during the third trimester.
6. Conflict of Interests Hadar Kesari-Shoham is employed by the manufacturer of the AL-SENSE panty-liner.
REFERENCES [1]
J. Bornstein, A. Geva, I. Solt, V. Fait, A. Schoenfeld, H. K. Shoham and J. Sobel, “Nonintrusive Diagnosis of Premature Ruptured Amniotic Membranes Using a Novel Polymer,” American Journal of Perinatology, Vol. 23, No. 6, 2006, pp. 351-354. doi:10.1055/s-2006-947159
[2]
J. Bornstein, G. ohel, Y. Sorokin, K. Z. Reape, O. Shmaider, H. Kessary-Shoham and E. Ophir, “Effectiveness of a Novel Home-Based Testing Device for the Detection of Rupture of Membranes,” American Journal of Perinatology, Vol. 26, No. 1, 2009, pp. 45-50. doi:10.1055/s-0028-1095183
[3]
L. Mulhair, J. Carter, L. Poston, P. Seed and A. Briley, “Prospective Cohort Study Investigating the Reliability of the AmnioSenseTM Method for Detection Of Spontaneous Rupture of Membranes,” An International Journal of Obstetrics and Gynaecology, Vol. 116, No. 2, 2009, pp. 313-
Copyright © 2011 SciRes.
309
318. doi:10.1111/j.1471-0528.2008.01828.x [4]
E. Jauniaux, D. Jurkovic, B. Gulbis, W. P. Collins, J. Zaidi and S. Campbell, “Investigation of Acid-Base Balance of Coelomic and Amniotic Fluids in Early Human Pregnancy,” American Journal of Obstetrics and Gynecology, Vol. 170, No. 5, 1994, pp. 1365-1369.
[5]
A. Greenough and M. Blott, “Neonatal Outcome after Prolonged Rupture of the Membranes Starting in the Second Trimester,” Archives of Disease in Childhood, Vol. 63, No. 10, 1988, pp. 1146-1150. doi:10.1136/adc.63.10_Spec_No.1146
[6]
A. Farooqi, P. A. Holmgren, S. Engberg and F. Serenius, “Survival and 2-Year Outcome with Expectant Management of Second-Trimester Rupture of Membranes,” Obstetrics and Gynecology, Vol. 92, No. 6, 1998, pp. 895901. doi:10.1016/S0029-7844(98)00287-7
[7]
J. U. Hibbard, M. C. Hibbard, M. Ismail and E. Arendt, “Pregnancy Outcome after Expectant Management of Premature Rupture of the Membranes in the Second Trimester,” The Journal of Reproductive Medicine, Vol. 38, No. 12, 1993, pp. 945-951.
[8]
R. B. Gold, G. L. Goyert, D. B. Schwartz, M. I. Evans and L. A. Seabolt, “Conservative Management of Second Trimester Post Amniocentesis Fluid Leakage,” Obstetrics and Gynecology, Vol. 74, No. 5, 1989, pp. 745-747.
[9]
A. F. Borgida, A. A. Mills, D. M. Feldman, J. F. Rodis and J. F. X. Egan, “Outcome of Pregnancies Complicated by Ruptured Membranes after Genetic Amniocentesis,” American Journal of Obstetrics and Gynecology, Vol. 183, No. 4, 2000, pp. 937-939. doi:10.1067/mob.2000.108872
IJCM
Diagnositic Methods for Amniotic Rupture of Membranes Test
Sensitivity Specificity
Pooling
Inaccurate/Subjective
False Positive
False Negative
Subjective
Nitrazine (pH)
90.70%
77.20%
17.40%
12.90%
Ferning (non laboring)
51.40%
70.80%
5-30%
12.90%
Ultrasound Amnio-dye Infusion Amnisure®
Al-SENSE™
CPT 83968(QW)
Does not detect ROM independently
Not reliable if used alone
“Gold Standard” for diagnosis of ROM
97.20%
98.00%
87.50%
~90%
PPV = 100% NPV = ~99%
Accuracy 96-100%
www.cs-commonsense.com
Shelf Life
Facts
NA ° Speculum Required 2 years ° Many Substances Interfere photosensitive ° Subjective NA
NA
NA
2 years
4 years
° Can only detect low levels of fluid (olygohydramnios: AFI index 5 or less) ° Requires expertise and time ° Highly invasive ° Expensive ° Requires expertise and time ° Complex- multiple step process ° invasive ° expensive & time consuming ° ° ° ° °
Easy-to-use panty liner non-invasive ° inexpensive instant results ° No color scale continuous monitoring available as a homet est
rev 12/11
