Eliminating unnecessary urine microscopy. Results and performance characteristics of an algorithm based on chemical reagent strip testing.

The ability of a urinalysis reagent strip to predict the presence of formed elements in the sediment was evaluated. The sensitivity of individual biochemical analytes varies from 0.51 to 0.85; however, the combined sensitivity of positive reactions for either protein, nitrite, leukocyte esterase, and/or hemoglobin is 0.95. Leukocyte esterase activity becomes detectable at a concentration of 15 white blood cells per high-power field (WBCs/HPF). Proteinuria is nonspecifically related to pyuria and detects a minimum concentration of 6 WBCs/HPF, and the hemoglobin reaction detects 6 red blood cells/HPF. Most false negative reactions are associated with bacteriuria. A positive chemical reagent strip test can be safely and effectively used as a prerequisite for routine urine microscopic examination.