Performance characteristics of dipstick and microscopic urinalysis for diagnosis of urinary tract infection

Abstract

Aim: Although the urine culture is used as the reference standard to determine presence or absence of urinary tract infection, the culture is an expensive and time-consuming method. The objectives of the study were to compare dipstick urinalysis with microscopic urinalysis and to compare dipstick and microscopic urinalysis results with urine culture results, by calculating performance characteristics of these tests. Method: The 250 morning urine specimens were performed by using dipstick and microscopic urinalysis and cultured. Laboratory urinalysis included semi-automated dipstick reading by a Miditron-M Reflectance photometer and microscopic examination. Result: Thirty-five point six percent (89/250) of patients had urine cultures with 105 colonies/mL or greater. Sensitivity and specificity of microscopic urinalysis were 91% and 68%, whereas in dipstick urinalysis they were 80% and 60%, respectively. Negative predictive values were 84% for urine dipsticks and 93% for microscopic urinalysis. Positive predictive values were 52% and 61% for dipstick and microscopic urinalysis, respectively. Conclusion: The study has suggested that both urinalysis methods can be used for rapid diagnosis. Urine culture is an expensive test for routine use and should not be applied unless the result of the nitrite, leukocyte or bloods are positive in dipstick or leukocyte, erythrocyte or bacteria are positive in microscopic examination.