Rapid cytologic diagnosis of Pneumocystis: a comparison of effective techniques

There has been a dramatic increase in pneumocystis carinii pneumonia (PCP) among patients with acquired immune deficiency syndrome (AIDS) and immunosuppression. Cytologic specimens including random and induced sputum samples, bronchoscopic washings, bronchoalveolar lavage, and fine needle and open lung biopsies can all be used for a rapid, accurate, and economical PCP diagnosis. Of these, bronchoalveolar lavage has emerged as the most diagnostic specimen, but the diagnostic yield of induced sputum is under investigation. Commonly used Gomori's methenamine and Gram-Weigert silver stains identify the cyst walls. Trophozoite forms can occasionally be stained by Gram Weigert, and specifically by Giemsa and PAS techniques. Organisms occur within the alveolar secretions inspissated in the form of foamy alveolar casts (FACs). PCP can also be identified in the Papanicolaou-stained pulmonary specimens. Alveolar proteinaceous material and cyst walls are stained pale gray and the nuclei as dark dots. Pap-stained PC cysts can be excited by ultraviolet light; they fluoresce and appear greenish yellow with irregular shapes, easily distinguishable from fungi. Organisms under ultraviolet stimulation must also be distinguished from cigarette smoker's pigment, red blood cells, and mucus. Following treatment, FACs persist, GMS-stained cysts are less numerous, fluorescence diminishes, and organisms become fragmented and may appear swollen. They may be seen within the macrophages and bronchial mucus secretion. We conclude that GMS, Gram-Weigert, and routine Papanicolaou staining are valuable for rapid PCP diagnosis. Besides PCP, associated infections and cellular changes can also be correctly diagnosed in Papanicolaou-stained specimens, including other infectious and neoplastic processes common in the AIDS victim.