Optimized urinary microscopy for assessment of bacteriuria in primary care.

Microscopy of wet-stained urinary sediment as an indicator of bacteriuria was evaluated in 418 consecutive primary care visits in a small community. Delivery of morning urine was encouraged and contributed to bladder incubation times of 4 or more hours in 79% of the visits; the overall culture positivity was about 80%. Bacteria or leukocytes alone or together as minimal requirements were suboptimal microscopy criteria for bacteriuria, whereas a minimum of moderate amounts of bacteria or 5 leukocytes per high-power field (x400) as a cutoff point yielded the best diagnostic accuracy. Optimization of urinary sediment microscopy in this way resulted in a desirable high sensitivity (97%) and efficacy (86%) in acutely symptomatic patients, as well as reasonably high efficacy (79%) in other patients, independent of sex or bladder incubation time. The method's simplicity and speed recommend it for use in primary care, particularly in patients with acute symptoms of urinary tract infection.