For Cryptococcus, antigen testing is the mainstay of diagnosis. The sensitivity in cryptococcal meningitis approaches that of culture while providing more rapid diagnosis (Perfect and Casadevall, 2002).
By contrast, IF staining of respiratory specimens for Pneumocystis jiroveci is one of several techniques of similar sensitivity for detection of Pneumocystis pneumonia. The choice of IF, conventional stain, or Calcifluor white depends on the laboratory. IF and Calcifluor require fluorescent microscopes, and IF reagents are expensive. Calcifluor and conventional staining methods require the reader to discriminate between Pneumocystis, yeasts, other pathogens, and cellular structures morphologically, which requires more interpretive skill than IF staining (Cruciani et al., 2002; Thomas et al., 2004).
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