title: A control system for monitoring the performance of leukocyte strip tests.
abstract: The control system described here is used to monitor the performance of urinary reagent-strip tests for leukocytes. The presence of leukocyte esterase in the urine is used as a marker for leukocytes in urine. The control system is based on sonicated leukocytes, isolated from whole blood. The esterase activity of this sonicate is determined by spectrophotometry with the N-tosyl-L-alanine ester of 5-phenyl-3-hydroxypyrrole as substrate. The assay result is used to determine the amount of sonicate needed to prepare buffered esterase-containing solutions. Such control solutions mimic leukocytic urines and are stable for 6 h at room temperature. The variability of the control system was tested by preparing it five times in a day on five separate days. The overall CV for Leukostix Reagent Strips (Ames Division, Miles Laboratories, Inc.) when tested with these solutions and analyzed with a reflectance spectrophotometer was 8%; for visual readings it was 10%. The overall CV for Chemstrip LN Reagent Strips (Biodynamics, Indianapolis, IN) was 10%.
mesh_terms: D002469:Cell Separation; D004950:Esterases / Q000032:analysis* / Q000592:standards; D006801:Humans; D007202:Indicators and Reagents / Q000592:standards; D007962:Leukocytes / Q000201:enzymology*; D011786:Quality Control; D011934:Reagent Strips / Q000592:standards; D012996:Solutions; D013010:Sonication; D013053:Spectrophotometry; D014556:Urine / Q000166:cytology
chemical_list: D007202:Indicators and Reagents; D011934:Reagent Strips; D012996:Solutions; D004950:Esterases