The conventional diagnosis challenge: Real-time PCR and nested PCR correlation with the scoring system for individuals at high-risk of Pneumocystis jirovecii pneumonia.

Introduction: Pneumocystis jirovecii is an opportunistic fungus that affects mainly people living with HIV (CD4 cell count lower than 200 cells/ml) and other immunosuppressed patients. Since P. jirovecii does not grow on routine mycological media, diagnosis of P. jirovecii pneumonia relies on indirect evidence of its presence in respiratory samples.

Objectives: To associate the results of direct immunofluorescence and two molecular methods with a score to predict P. jirovecii pneumonia in patients with AIDS.

Materials and methods: A prospective study was conducted with 40 patients. A respiratory sample collected before treatment was subjected to direct immunofluorescence using the Merifluor kit, to nested PCR targeting the mitochondrial large subunit ribosomal RNA, and to the VIASURE real-time PCR kit.

Results: These three techniques revealed P. jirovecii in 6, 12, and 15 samples, respectively. All positive samples by direct immunofluorescence were positive by nested PCR, and all positive samples by nested PCR amplified by real-time PCR. There was a statistically significant association between the P. jirovecii pneumonia score and the molecular methods. Two patients were early diagnosed and responded well to treatment.

Conclusion: Molecular methods, especially real-time PCR, are recommended for early diagnosis of P. jirovecii pneumonia in AIDS patients.