ACCEPTABILITY OF LOW-VOLUME, INDUCED SPUTUM SPECIMENS FOR DIAGNOSIS OF PNEUMOCYSTIS-CARINII PNEUMONIA

Two milliliters of induced sputum is the minimum volume recommended fo r microscopic examination for Pneumocystis carinii by direct fluoresce nt antibody (DFA) stain. Many specimens received in our laboratory do not meet this criterion. Rejection of these inadequate specimens incre ases cost and discomfort to the patient because additional specimens m ust be obtained. To determine whether volumes less than 2 mL were acce ptable for microscopic analysis, we examined 177 consecutive induced s putum specimens submitted for P carinii DFA stain. Eighty-four (47.4%) specimens were less (0.5-1.9 mL) than the 2-mL volume recommended by the manufacturer. Overall, 33 specimens were positive. The positivity rates for specimens 2 mL or more and less than 2 mL were 18% and 19%, respectively. Induced sputum volumes between 0.5 and 2 mL may be accep table for DFA examination.