[Peroxidase activity of urinary cell elements, leucocyturia and urinary tract infection]

Abstract

Peroxidase activity determination of urinary formed elements is proposed as a new leucocyturia detection method. Enzymatic activity is evidenced by hydrogen peroxide 0.54 mM in Trinder reagent. The reaction can be performed in filtrative microplate or in standard microplate. Results are formulated semi-quantitatively or using arbitrary units (UA/ml) respectively. Reproducibility of the peroxidase activity assay (n = 31, m = 754 UA/ml, CV = 6.8%) is higher than microscopic evaluation methods (direct microscopic examination: n = 31, m = 3, CV = 66%; standard sediment method: n = 31, m = 7, CV = 71%). Urine conservation is suitable during about 20 hours at 4 degrees C. In case of microscopic hematuria (less than 1.5 x 10(6) red blood cells/ml) only few interference was observed. On the other hand, macroscopic hematuria may be inhibitory for the enzymatic reaction. Peroxidase activity determination, microscopic leucocyte count and bacterial numeration were performed on 2,004, 1,589 and 1,709 urine samples, respectively. The low correlation between peroxidase activity and microscopic leucocyte count is discussed. This new enzymatic method contributes to detect urine samples with significant bacteriuria (greater than or equal to 10(5) UFC/ml): about 90 p. cent sensitivity and 95 p. cent negative predictive value.