A comparison of modified methenamine silver and toluidine blue stains for the detection of Pneumocystis carinii in bronchoalveolar lavage specimens from immunosuppressed patients.

Pneumonia due to Pneumocystis carinii is an increasingly frequent occurrence; a prompt, accurate diagnosis is important to successfully manage this infection. Methenamine silver and toluidine blue stainings of material recovered by bronchoalveolar lavage (BAL) have been the most widely employed techniques for detecting Pneumocystis organisms. The value of these two staining techniques for the detection of Pneumocystis organisms was prospectively compared in 220 BAL specimens obtained from 186 immunosuppressed individuals. The patients included those with disease-related and therapy-related immunosuppression; half of the BAL specimens came from organ transplant recipients. The results indicate that neither method is superior to the other and that both will correctly identify almost all Pneumocystis infections if a sufficient aliquot of BAL material is examined systematically by trained individuals. The toluidine blue method is somewhat simpler to perform, however. The reasons for discrepant results between the two staining methods were analyzed.