ever, John et al. (2) recently ... John R, Henley R, Shankland D. Concentrations of free thy- roxin and ... Allan DJ, Murphy F, Needham CA, Barron N, Wilkins TA,.
Table 1. Components of Variance, index of Individuality (CVI/CV0), and Minimal Significant Difference for Two Consecutive Results (d) for Zn, Cu, and Mg Element Zn, .miol/L Cu, 1zmol/L Mg, mmol/L
Mean (n = 15)
V (CV,, %)
13.3
0.03 (1.4) 0.01 (0.9) 5.3 iO- (0.7)
14.4
0.83
V1(CV1,%)
VO(CVO, %)
1.5 (9.3) 0.65 (5.6) (3.4) 1.2’ i0
difference between the results from sequential specimens will be required for them to be significantly different.
CV1/CV0 0.98
1.6 (9.4) 3.8 (13.6) 5.8’ iO (7.3)
d 3.4
0.41
2.3
0.46
0.1
0,20
References 1. Browning MCK, Ford RP, Callaghan SJ, Fraser CG. Intra- and interindividual variation of five analytes used in assessing thyroid-function: implications for necessary standards of performance and the interpretation of results. Clin Chem 1986;32:962-6. 2. Sprague S, Slavin W. Determination of iron, copper, and zinc in blood serum by atomic absorption method requiring only dilution. At Absorp Newsl 1965;4:228-36. 3. Fraser CG. Analytical goals are applicable to all. J Int Fed Clin Chem 1990;2:84-6. 4. Harris EK. Effects of intra- and interindividual variation on the appropriate use of normal ranges. Clin Chem 1974;20:1535-42.
-J
0
E E 0,10 U
U U,
0,00
Effect of Storage Conditions on Salivary SIalic Acid Concentrations, Francoise Callais,1 Michel Bouchoucha,2 Paul-Henri Cugnenc,2 Jean-Philippe Barbier,2 and Ohvanesse Ekindjian1 (1 Lab. Central de Biochim., and 2Dept. de Gastroenterol., H#{244}pital La#{235}nnec, 42 Rue de S#{232}vres, 75007 Paris, France) Salivary mucins contribute to the protection of the esophageal mucosa by forming a viscoelastic gel that serves as a physical barrier against environmental agents such as refiuxed gastric acid (1). Salivary mucin content can be estimated by measuring concentrations of glycoproteinbound sialic acid, which has been proposed as a marker of salivary participation in esophageal acid clearance. We report the results of a study concerning the optimal storage conditions of saliva samples before such analysis. Resting salivary secretions were collected from 25 healthy subjects [eight men and 17 women, mean age 36 (SD 5) years] between 0900 and 1100 h after a 3-h fast. Over a 1-h period, the subjects allowed saliva to accumulate in the mouth for each 30 s and then expelled it into a flask. The mean volume collected was 32 (SD 5) mL. The specimens were homogenized by vortex-mixing and then aliquoted into screw-capped tubes (500 FL/tube). Equal numbers of tubes were stored at -20 #{176}C and 4#{176}C. Samples were analyzed immediately after the collection and 1,5, 10, 20, and 30 days later. Sialic acid was quantified by the method of Aininoff (2), with N-acetylneuraminic acid (Merck, Dai-mstadt, F.R.G.) as standard. The concentration of glycoprotein-bound sialic acid was taken as the difference between the concentration of total sialic acid (i.e., free plus bound) measured after acid hydrolysis (with H2S04, 0.5 molIL, at 80#{176}C) and that of free sialic acid measured directly. Because the concentration of sialic acid increased during the first 45 mm of acid hydrolysis, then remained stable for the following 2 h, we hydrolyzed the samples for 60 mm. The data were examined by analysis of variance (ANOvA). Total sialic acid concentrations in saliva stored at 4 or -20 #{176}C did not change with time. Similarly, free sialic acid
0
10
20
30
TIme (days) Fig. 1.Changes with time in free sialic acid (FSA) and total sialic acid (TSA) concentrations in saliva stored at 4#{176}C The concentration of mucin-boundsiaticacid (BSA) represents the difference between TSA and FSA.Valuesare shownas mean ± SEM(n = 25)
concentrations remained stable during the 30-day storage period at -20 #{176}C. In contrast, at 4#{176}C the concentration of free sialic acid increased significantly with time (Figure 1) (P
