Background: Urine culture is still the standard laboratory procedure for definitive diagnosis of urinary tract infection. The author investigated the feasibility of eliminating the costs and time expended in examination of negative urine cultures by combining the Sysmex UF-100 (Toa Medical Electronics, Kobe, Japan) urine flow cytometer and urine strips to predict the outcome of urine cultures.

Methods: Seven hundred eighty one specimens were obtained from 661 males and 120 females (mean age, 66 years; range, 4~93 years). Urine cultures were performed with 10,000 colony forming units (CFU)/mL as the positive criterion. Each sample was analyzed by Clinitek Atlas (Bayer Co., Elkhart, IN, USA) using N-multistix SG urine strips, followed by identification and quantification of the formed elements on the Sysmex UF-100.

Results: Of the 781 urine specimens examined, 402 (51.5%) yielded positive cultures. The diagnostic performance of the UF-100 results for bacteria or WBC vs the urine strip results for leukocyte esterase or nitrite in comparison with the urine culture results were as follows: sensitivity 0.88 vs 0.80, specificity 0.77 vs 0.77, positive predictive value 0.80 vs 0.78, and negative predictive value 0.85 vs 0.79. The highest sensitivity (0.91) and the lowest false negative (0.05) were obtained when any one of the four tests was positive.

Conclusion: The use of Sysmex UF-100 flow cytometer and urine strip results, seperately or in combination, does not accurately predict the outcome of urine cultures. (Korean J Clin Microbiol 2006;9(1):30-35)