To the Editor.—
The leukocyte esterase dipstick (Chemstrip 9) has been shown to be a sensitive screening test for pyuria and hematuria in symptomatic1 and asymptomatic2 patients. In an attempt to develop a cost-effective approach to this problem in a university health service, all female patients complaining of dysuria were screened with the dipstick. One hundred consecutive symptomatic females were screened from August 1985 through November 1985. The dipstick results were compared with microscopic examinations and culture results. Leukocyte chamber counts were not obtained because this test is not routinely available in most primary care ambulatory settings.
Report of a Study.—
Four patients reported taking phenazopyridine hydrochloride (Pyridium) within 24 hours of the laboratory evaluation. Two (50% ) of the four urine specimens had negative leukocyte esterase readings, with microscopic urinalyses showing 13 and 17 white blood cells per high-power field (WBCs/hpf). Culture results showed more than 100 000
Kerr JE, Magee-Nolan C, Schuster BL. Interference by Phenazopyridine With the Leukocyte Esterase Dipstick. JAMA. 1986;256(1):38-39. doi:10.1001/jama.1986.03380010042017