Reagent strip screening for sediment abnormalities identified by automated microscopy in urine from patients suspected to have urinary tract disease.

We assessed the ability of reagent strip screening to predict the finding of blood cells and bacteria using an automated urinalysis workstation (The Yellow IRIS, International Remote Imaging Systems, Chatsworth, Calif) in 427 specimens submitted for urine culture. The sensitivities of leukocyte esterase, hemoglobin, and nitrite detection on reagent strips were 71.9%, 70.8%, and 56.7%, respectively, at 5 or more white blood cells per high-power field, at 3 or more red blood cells per high-power field and bacteria observed using the IRIS. Screening results for leukocyte esterase associated with negative results using the IRIS for white blood cells represented mostly false-positive screening test results based on chart review. Positive screening test results for hemoglobin associated with negative results obtained with the IRIS for red blood cells consisted of equal numbers of false-positive screening test results and IRIS test results based on chart review. A common screening algorithm using a combination of these three reagent strip variables exhibited a false-negative rate of 30.1%: review of medical records found clinical evidence of urinary tract infection in 14 patients and genitourinary or renal disease or hypertension in another 13 patients. Adding more variables to the algorithm increases the sensitivity and decreases the specificity. Both microscopic examination and reagent strip testing of urine are necessary for the detection of abnormalities associated with disease.