comparison of gomori’s methenamine silver method with pcr technique on oral swab, bronchoalveolar lavage and lung ho-mogenate specimens in detection of pneumocystis

background: pneumocystis carinii is one of opportunistic organisms especially in immuno-compromised patients. for years, diagnosis of pneumocystis pneumonia (pcp) has relied on microscopic visualization of organism in specimens obtained from the lung either by bronchoalveolar lavage (bal) or by induction of sputum, but failed to provide efficient diagnosis. the aim of this study was to compare of pcr result and gomori's methenamine silver (gms) of invasive and noninvasive specimens in infected rat. methods: thirteen stimulated rat with methylprednisolone acetate used as test group and 4 non-stimulated rats were used as control group. oral swabs (os), bal and lung homogenate (lh) specimens were collected from weeks 0, 2, 4, 5, 6 and 7. all samples were tested with (gms) staining method and pcr technique.  results:   the results showed the sensitivity of pcr method higher than gms (69.2% versus 0%) in oral swab samples (p> 0.001). the analysis of the results also proved that pcr test using noninvasive oral swab had comparable results with the gms staining method on invasive lung biopsy specimens (69.2% versus 61% and 84.6 for bal and lung biopsy). conclusion: higher sensitivity of pcr using noninvasive sample can made it a useful method in rapid diagnosis of pcp.