Precision data by laboratory technologists on ward 8 separated by sensor lot no.â Lot no. Ranges. CV, % .... medical technologists involved in the process were ...
Table 1. Precision data on control samples obtained with the Ames Glucometer eight wards compared with laboratory staff.a
Elite and the M+ by nurses on
Nursing staff Glucometer Elite
Ward
CV, %
1
8.7
M+
x, mmol/L 4.9
11.5
Elite
2
Elite
3
M+ Elite
4
M+ Elite
5
M+ Elite
6
M+ Elite
7
M+ Elite
8
M+ Elite M+
Aggregate Aggregate
‘ C
CV, %
,?, mmol/L
n
5.2
4.7
23
119
7.2
6.3
52
488
7.8
4.9
21
10.1
6.2
317
5.6
6.3
34
8.5
4.8
201
7.4
4.9
20
8.8
6.2
220
7.3
6.1
35
8.4
4.7
387
4.2
4.9
17
10.7
6.1
365
6.8
6.1
34
8.8
4.8
222
6.1
4.8
24
8.6
6.2
263
5.0
6.0
33
8.7
4.8
499
6.9
4.8
23
9.2
6.1
325
7.2
6.1
35
8.5
4.9
333
5.9
4.9
22
8.6
6.4
271
6.7
6.2
31
9.2
4.9
1713
5.7
4.9
327
9.2
6.3
981
7.1
6.0
186
8.8 9.5
4.9 6.2
3949 2861
5.8 7.1
4.9 6.1
477
Lot no.
a
n 106
6.4
Precision data by laboratory technologists Elite
staff
4.9
8.3
M+
Laboratory
Ranges
420
on ward 8 separated by sensor lot no.” CV, %
i, mmol/L
n
4B0
4CA
4.0-5.7
4.6
4.6
32
4B0
4DA
4.1-5.8
4.3
4.9
81
4B0
5GA
4.4-6.2
4.7
5.0
116
4C0
5BB
4.4-6.2
5.4
5.0
73
4F0 55A
4.3-6.1
5.2
4.9
5.2
4.9
Aggregate Obtained over 1.5-year period.
89 391
Gathered subsequentto a, from November 1994 to March 1995. Specified by Ames for the indicated sensor lot no.
to be rushing this step. Proper training and careful attention to technique is required, especially when nonlaboratory staff perform the testing (5). The betterprecision achieved by trained contention.
laboratorians
is consistent
with
this
The number of “strips” used on the wards by the nursing staff decreased to 33 750 per year for the Elite from 50 400 per year for the M+. The corresponding cost was decreased to $21 640 (Can) for the Elite from $31 510 (dan) for the Glucometer M +. Approximately the same number of patients was tested over the same period in both groups: 20 074 patients for the Elite and 21 310 for the M+. The number of QC checks, run in both time periods, was approximately the same at 3865 for the Elite and 4571 for M+. The total number of Glucometer usages for both the Elite and the M + were therefore, respectively, 23 939 and 25 881. However, the total numbers of strips, as indicated above, were 33 750 for the Elite and 50 400 for the M+, which indicates that multiple strips were used during each usage either because of technique failures or QC failures. This amounted to 1.34 Elite strips per use (33 750/23 935) compared with 1.95 strips per use (50 400/ 25 881) for the M+ and confirmed our impression that the Elite required significantly fewer repeat strips during routine use than the M This certainly agrees with the frequent complaints by the nurses about the difficulty of use of the M + as opposed to the satisfaction expressed for
the Elite, both in terms of ease of use and confidence reported results.
in the
References 1. Jones BA. Testing at the patient’s bedside. Clin Lab Med 1994;14:473-91. 2. Innanen VT, Korogyi N, Ambus T. A practical approach to the bedside use of glucose monitoring. Can J Med Technol 1988;50: 146-51. 3. Innanen VT, Korogyi N, Mellor N, Kenshole A. Bedside monitoring of the blood glucose level: the high cost of reliable results. Can Med Assoc J 1989;140:899-901. 4. Koschinsky T, Dannehl K, Gries FA. New approach to technical and clinical evaluation of devices for self monitoring of blood glucose. Diabetes Care 1988;11:619-29. 5. Kaplan LA. NACB special conference on point-of-care testing.
Four Automated Random-Access Immunoassay Analyzers Evaluated for Thyroid Function Testing, Mohammad Amin Abubaker, Dianela Y. Fibs, and J. R. Petersen’ (Dept. of Pathol., Univ. of Texas Med. Branch, Galveston, TX 77555-0742; 1 author for correspondence: fax 409-772-9245)
+.
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Vol. 41, No. 10, 1995
We evaluated four instruments-Technicon Immuno 1 (Bayer, Diagnostics Div., Tarrytown, NY), Access (Sanofi
Pasteur, Chaska, MN), Vista (Syva, San Jose, CA), and ACS:180 (Ciba-Corning, Norwood, MA)-for measurement of thyroxine (T4), triiodothyronine uptake (T3-U), and thyroid-stimulating hormone (TSH). The instruments offer: (a) minimal manipulations of samples and reagents; (b) barcode technology to identify samples, reagents, calibrators, and quality-control (QC) material; (c) bidirectional interface with the laboratory information system (US); and (d) an onboard menu that covers frequently ordered immunoassays. The Immuno 1 and Access also offer stat interrupt capability. The results obtained with these analyzers were compared with those from commercial RIA methods-TSH (Nichols Diagnostic, San Juan Capistrano, CA), T4 (Incstar, Stillwater, MN), T3-U (Binax, Portland, ME)-routinely used in-house. Here we summarize the result of the evaluation of these instruments. All four random-access immunoassay analyzers (RAIAs) were installed in-house and calibrated according to each manufacturer’s protocol. Before the evaluation, medical technologists involved in the process were either trained in-house (ACS:180 and Vista) or at the manufacturer’s training center (Immuno 1 and Access). Technicon Immuno 1 uses a heterogeneous magnetic separation enzymatic assay with colorimetric detection of the reaction product for TSH and T3-U assays and a homogeneous latex agglutination assay for T4. Access uses a paramagnetic particle solid phase to separate bound analyte from free, followed by an alkaline phosphatasetriggered aryloxide dioxetane chemiluminescence. The chemiluminescence signal so generated is constant, in contrast to the flash of light observed in the hydrogen peroxide-generated acridinium chemiluminescence in the ACS:180 (1,2). The Vista immunoassay system uses heterogeneous competitive and sandwich-type assays and detects alkaline phosphatase-labeled antigen or antibody by use of 4-methyl umbelliferyl phosphate substrate (3). The ACS:180 (4) uses hydrogen peroxide-generated acridinium chemiluminescence with paramagnetic particles to separate bound from free analyte. The negligible background noise in chemiluminescence detection used for both the ACS:180 and Access renders the assays extremely sensitive, being about fivefold as sensitive for T4 and TSH as the Immuno 1 and Vista. We analyzed 100 serum samples collected in red-top SST tubes (Becton Dickinson, Rutherford, NJ) for T4 (RIA range 35-182 g/L), T3-U (RIA range 0.6-1.4), and TSH (RIA range 6 g/L lipids, none of the assays showed significant interference up to 12 gfL lipids, as defined by a change of concentration >1 SD of the expected value. Assessments of nonlinearity, drift, and carryover were made by multiple linear regression, the statistical calculation of which is simplified by using the experimental design outlined in the NCCLS protocol (5), i.e., running controls over a 10-day period. All instruments gave linear results, and no carryover or drift could be detected. Nonparametric statistics were used to compare the RIA results with those of the various RAIAs. The slope and the intercept for the nonparametric regression line were calculated by using Theil’s incomplete method (6). In general, TSH gave the best RIA vs RAIA (Table 1) and interRAlA comparison (data not shown), followed by T4 and T3-U. The lower correlation coefficients for T4 and T3-U are related to the narrow concentration range covered, especially for T3-U because of nonavailability of serum samples to cover the full calibration range. Interestingly, all the RAIA results showed better correlation with the RIA results than among themselves, thus highlighting the RAIAs’ differences in principles, antibodies, and assay protocol. TSH compared best with the RIA and also intercompared best among the RAJAs. The means of all patients’ results for T4 and T3-U differed significantly for the different RAIAs. The within- and between-run CVs for RAIA (1-9%) were considerably better than those for the RIA (8-14%). TSH on all instruments had a functional sensitivity (detection limit) of 0.99 with slopes ranging from 0.99 to 1.01 andy-intercepts of -0.01 to 0.01. ACS:180 was the fastest analyzer, followed by Access, Immuno 1, and Vista. Walkaway reliability was evaluated by setting up overnight runs on 3 days. Except for Vista, the RA.IAs showed error messages on the evening runs that required medical technologist intervention. None of the instruments had major maintenance problems during the 3-month evaluation period. We conclude that each of these analyzers has a place in the clinical laboratory, depending on individual requirements, e.g., space (Access has the smallest footprint), speed (ACS: 180 will give results 2-3 times faster than the other analyzers), length of calibration (Immuno 1 requires
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at least 25% fewer calibrations), or reliability the fewest problems in our study).
(Vista had
References 1. Schaap A?, Akhavan H, Romano L,J. Chemiluminescent substrates for alkaline phosphatase: application to ultrasensitive enzyme-linked immunoassays and DNA probes. Clin Chem 1989;
35:1863-4. 2. Dudley RF. Chemiluminescence immunoassay. to RIA. Lab Med 1990;21:216-22. 3. Meyer B, Diaco R. Application magnetic particles to immunoassay 1987;33:1543-7.
of novel
An alternative
chromium
development.
dioxide
Clin
Cheni
4. Dudley RF. The Ciba Coming ACS:180 automatedimmunoas say system. J Clin Immunoassay 1991;14:77-82. 5. National
Committee
of Clinical
Laboratory
Standards.
EF
10-T. Preliminary evaluation of clinical chemistry method; tenta tive guideline. Villanova, PA: NCCLS, 1989. 6. Miller JC, Miller JN, eds. Statistics for analytical Vol. 2. New York: Ellis Horwood, l988:l55pp.
chemistry,
