Quantitative urine test strip reading for leukocyte esterase and hemoglobin peroxidase.

BACKGROUND: Recently, urine test strip readers have become available for automated test strip analysis. We explored the possibilities of the Sysmex UC-3500 automated urine chemistry analyzer based on complementary metal oxide semiconductor (CMOS) sensor technology with regard to accuracy of leukocyte esterase and hemoglobin peroxidase results. We studied the influence of possible confounders on these measurements. METHODS: Reflectance data of leukocyte esterase and hemoglobin peroxidase were measured using CMOS technology on the Sysmex UC-3500 automated urine chemistry analyzer. Analytical performance (imprecision, LOQ) as well as the correlation with white blood cell (WBC) and red blood cell (RBC) counts (Sysmex UF-5000) were studied. Furthermore, the influence of urinary dilution, haptoglobin, pH and ascorbic acid as confounders was determined. RESULTS: Within- and between-run imprecision (reflectance signal) ranged from 1.1% to 3.6% and 0.9% to 4.2% for peroxidase and 0.4% to 2.5% and 0.4% to 3.3% for leukocyte esterase. Good agreement was obtained between the UF-5000 for RBCs and peroxidase reflectance (r=0.843) and for WBCs and leukocyte esterase (r=0.821). Specific esterase activity decreased for WBC counts exceeding 100 cells/µL. Haptoglobin influenced the peroxidase activity, whereas leukocyte esterase and peroxidase activities showed a pH optimum between 5.0 and 6.5. A sigmoidal correlation was observed between urinary osmolality and peroxidase activity. CONCLUSIONS: CMOS technology allows to obtain high quality test strip results for assessing WBC and RBC in urine. Quantitative peroxidase and leukocyte esterase are complementary with flow cytometry and have an added value in urinalysis, which may form a basis for expert system development.

[Peroxidase activity of urinary cell elements, leucocyturia and urinary tract infection]. / Activité peroxydasique des éléments figurés urinaires, leucocyturie et infection urinaire.

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.

Comparative analysis of the concentration of injected horseradish peroxidase in cytoplasmic granules of the kidney cortex, in the blood, urine, and liver.

The concentration of horseradish peroxidase in total particulate fractions from the kidney cortex did not change much during the first few hours after injection, as long as most of the injected protein was not yet cleared from the blood. It decreased at a rate of 6-8% per hr afterwards. The concentration of peroxidase in total particulate fractions increased in proportion to the load (dose) over a wide range, suggesting that a constant fraction of the protein was reabsorbed by micropinocytic vesicles into the tubule cells from the glomerular filtrate. The amount of peroxidase excreted in the urine also increased in proportion to the injected dose. The proportion of peroxidase taken up by the liver, however, decreased several times when the dose was increased. A marked decrease of protein uptake into the kidney cortex and an increase of urinary excretion were observed when rats received a second, equal dose of peroxidase 4 hr after the first injection, and the rate of clearance of peroxidase from the blood was decreased after the second injection. The liver, on the other hand, took up almost twice as much peroxidase after two injections as after one. The uptake of peroxidase by the kidney cortex increased with age. Cytochemical observations on the preferential absorption of peroxidase by certain cell types and segments of the renal tubules in relation to dose are reported.