Application of urine dipstick and smear Gram-staining microscopic examination tests in screening of urinary tract infection

Objective To compare the reliability of a urine dipstick evaluation for leukocyte esterase(LE) and nitrite (NIT) activity and smear Gram staining microscopic examination with the urine culture in diagnosing urinary tract infection (UTI). Methods 10 μl of clean catch midstream urine specimen was examined by culture, the other portion was tested with dipstick for presence of LE, NIT and for smear Gram staining microscopic examination. Results In 400 patients, 41(10.3%) showed culture positive. Comparing to the culture examination, the sensitivities of LE and NIT were 73.2% and 46.3% respectively, and the specificities were 86.6% and 98.1% respectively. The sensitivity and speciticity for the two tests combined were 90.2% and 85.2% respectively. The sensitivity of microscopic examination was 61.36%. Conclusions Urine dipstick test and smear Gram staining microscopic examination are not sufficiently sensitive to be used in the screening for UTI. Bacteriuria culture must be done in diagnosing UTI.