Usefulness of microscopic examination in urinalysis.

The authors evaluated 500 patients who yielded urine specimens containing red and white blood cells but that gave negative reagent test strip reactions to determine the medical usefulness of the microscopic examination in such cases. Half of the patients had a history of, or current signs and symptoms of genitourinary or renal disease (GURD), or had indwelling catheters, hypertension, or diabetes. The other half did not display these conditions. Red blood cells occurred rarely, and no red blood cell associated GURD was detected in these patients. Five had lower urinary tract infection. Seventy-two underwent further workup, but no GURD was found. Physicians did not comment or take action on the report in other patients. The authors found the test for leukocyte esterase and nitrite (LN) to have a predictive value for a negative result of 97% for exclusion of bacteruria. Based on these observations, the authors established in 1982 a policy that microscopic examination would be performed only on specimens negative by reagent test strip (including LN) if a "diagnostic urinalysis" (DU) was ordered. The authors recommended that DU be requested only for patients suspected of GURD. This has eliminated microscopic examinations on 25% of specimens and reduced costs.