Klinische Chemie Stichting Klinisch Chemisch Laboratorium Nucleaire Klinische

Klinische Chemie Stichting Klinisch Chemisch Laboratorium Nucleaire Klinische Geneeskunde Fysica Postbus 850 NL 8901 BR Leeuwarden Evaluation of a semiquantitative dipstick for the determination of microalbuminuria A. J. Bakker, D. Jager, G. Dijkstra Introduction: Patient comparison (n=188): Microalbuminuria is an important risk indicator for the development of diabetic nephropathy and cardiovascular diseases. Reliable semi-quantitative methods (applicable for primary healthcare) allow easy and much earlier detection. Here, we report an evaluation of the semiquantitative Immunodip dipstick test supplied by DCL. Patients: 205 patients (n=205) who subsequently supplied urine samples for determination of microalbuminuria were enrolled in this study. Analysis took place on the day the urine was delivered to the laboratory. Methods of analysis: The DCL Immunodip method (Menarini; prod. no. : 700 -01) for determination of microalbuminuria was performed according to manufacturers’ instructions. Results were divided in 5 classes: <12 mg/l (negative); 12 -18 mg/l (threshold); 20 mg/l, 40 mg/l and 80 mg/l (positive). Stability of the colour after reading was checked after 1, 3, 7 and 30 days. Quality control was performed with a negative urine and a low (± 18 mg/l) and a high (± 80 mg/l) control based on a saline diluted standardserum (DAKO X 0908). Analysis of microalbumin and creatinine was performed using a Modular anlyzer (Roche): Microalbuminuria was determined using a home-made procedure in which urine was mixed with phosphate buffered PEG 6000 buffer (10 mmol/l phosphate, p. H=7. 4, 4. 5% PEG-6000). After 5 min a 10 -fold diluted DAKO anti-humanalbumin antiserum (Q 328) in phosphate buffered saline started the reaction (volume sample/buffer/antiserum: 10µl/216µl/36µl; ref. value 16 mg/l). Creatinine: the Jaffé method (rateblanked and compensated) was used according to the Roche instructions (Roche, prod. no. : 1875418). Albumine-creatinine ratio was calculated from corresponding results (ref. value for men 1. 8 g/mol and for women 2. 5 g/mol). Sensitivity: 98. 0%; Specificity: 89. 1% Likelihood ratio: LR+: 8. 9; LR–: 44. 5 Sensitivity: 90. 4%; Specificity: 86. 7% Likelihood ratio: LR+: 6. 8; LR– : 9. 0 Stability: Colourstability Immunodip: Within-run reproducibility of the DCL Immunodip teststrips was tested with a control (diluted serum) at an albumin concentration of 18 mg/L. Between-run reproducibility was tested using control samples every day when analysis were The colour of the DCL Immunodip teststrips remains stable at room temperature. The interpretation of the majority of the samples did not change after 1, 3, 7 and 30 days for 96. 1%, 95. 6% and 77. 9% of the strips. The colour changes resulted in a higher outcome except for 5 (2. 4%) samples which had a borderline result on the first day and a negative result after day 1 -30 (graph shown below). performed (results shown by graphical representation). 80 within / between day 17 80 1 8 40 1 20 12 -18 neg 8 9 2 2 1 14 1 5 136 Conclusion The Immunodip dipstick for microalbumin reliably detects albumin concentration (relation with albumin-creatinine ratio as expected is less good). This Immunodip dipstick is suitable for reliable exclusion of microalbuminuria (Sacks et al. Clin Chem 2002; 48: 436 -472), but positive results should be confirmed by a quantitative procedure. The colour of the Immunodip dipstick remains stable for at least a week.