Predictive Value of Urine Microscopy in Urinary Tract Infections

M. Bonadio
1979 Nephron  
Dear Sir, Both conventional and simplified urine culture methods have the disadvantage of requiring 18-24 h of incubation before the result is available. Rapid detection of significant bacteriuria is particularly useful when life-threatening generalized sepsis is suspected to arise from the urinary tract. This would allow prompt and appropriate antimicrobial treatment. In general practice, attendances for symptoms suggesting acute urinary tract infection are relatively frequent. 50% of women
more » ... nt. 50% of women complaining of symptoms of urinary infection have been reported to have true bacterial infection, whereas the remainder are suspected to have nonspecific urethritis [1]. Most general practitioners do not use urine cultures (or appropriate substitutes) to diagnose urinary tract infection. Microscopy of fresh, unspun urine is one routine procedure used in some clinics and has proven to be an aid to detection of bacteriuria in children [2]. In order to evaluate the reliability of such a procedure in situations where the expected percentages of significant bacteriuria is high, we compared urine microscopy with the conventional pour-plate method on a series of patients at high risk of urinary tract infection. From February 1977 to January 1978,165 urine specimens were obtained from 140 females and 25 males (120 outpatients attending our urinary tract infection clinic and 45 patients admitted to our general hospital because of various urological diseases). All patients were given careful spoken instructions for collection of their clean voided midstream urine specimen. Only 30 specimens were collected by single urethral catheterization or from an indwelling catheter. In all cases, the urines were allowed to stay in the bladder for at least 4 h. 48 patients were on antimicrobial therapy at the time of urine collection, whereas all the others had not been taking any antimicrobial drugs for at least 7 days. Each specimen was immediately processed (normally within 30 min of collection, in all cases no later than 1 h). All urines were cultured in nutrient agar using the standard pour-plate method at dilutions of 10_1 and 10-3. All the 165 urine specimens were evaluated by microscopy: a drop of well-mixed, unspun urine was placed on a slide, covered with a cover slip and examined with high dry lens (400 ×) for bacteria, white cells and red cells. 20 randomly selected fields were searched under reduced light. The number of bacteria was expressed as 1 + (few) when the rods seen by microscope ranged from at least 2/20 fields to 3/field, or 2+ (many) when more than 10 rods/field were detected. Leukocyturia and hematuria were defined > 5 WBC/20 fields and > 1RBC/20 fields, respectively. Urines were considered infected when more than 105 colonyforming units (CFU)⁄ml urine of a single organism were recovered on culture by the pour-plate method. 77 urines were found to be infected according to the mentioned criterion. 60 of these showed more than 106 colonies/ml urine on culture. The causative isolates of infected urines were
doi:10.1159/000181694 pmid:492420 fatcat:veuqnqv75zcnxocne75rhygg3m