LABORATORY EVALUATION OF URINARY-TRACT INFECTIONS IN AN AMBULATORY CLINIC

A 4-month evaluation of ambulatory patients with a suspicion of a urin ary tract infection was performed. Specific objectives included assess ment of five urinary screening methods, reevaluation of the necessity of the phenylethyl alcohol plate (PEA), and cost-effectiveness of scre ening for low colony count bacteriuria. Urine samples were collected a s midstream, clean-caught specimens. A total of 142 samples, 87 from 7 9 symptomatic patients and 55 negative controls, were evaluated. All u rine specimens were cultured using a 0.01 mL loop and a 0.001 mL loop onto Columbia sheep blood agar, MacConkey agar, and PEA agar. Twenty-f our specimens (17%) were sterile, 64 (45%) were contaminated, and 54 ( 38%) were infected. Five urine screening methods were performed. These tests and their associated sensitivity and specificity are as follows . The Chemstrip 9 (Behring, Inc., Somerville, NJ) for leukocyte estera se and nitrate, 67%, 98%; microscopic analysis on spun urine, 79%, 93% ; methylene blue stain for pyuria, 60%, 99%; Gram stain for pyuria, 45 %, 93%; Gram stain for bacteriuria, 65%, 75%; and the URISCREEN (Analy tab Products, Plainview, NY), 92%, 89%. Inclusion of a PEA plate for i solation of gram-positive organisms provided no additional information . Routine culture of urine samples at 10(-2) mt increased the contamin ation rate by 19%.