Use of a semiquantitative microscopic method for detecting bacteriuria.

We evaluated a microscopic examination for bacteriuria, performed by experienced observers and by 25 house officers who were less practiced in the technique. Simulated urine samples containing known concentrations of Escherichia coli with or without polymorphonuclear leukocytes were examined uncentrifuged in a wet mount with a methylene blue stain. The experienced observers were able to determine whether a sample contained greater or less than 10(5) organisms per milliliter with a high degree of sensitivity and specificity. The house officers demonstrated a lessened discrimination, and leukocytes in the samples altered their decisions as to whether samples contained significant numbers of bacteria. Experienced observers can successfully use the microscopic examination as a rapid and inexpensive diagnostic tool to diagnose significant bacteriuria.