RESUMEN
OBJECTIVE: The prevalence of Pneumocystis jirovecii colonization and its role in pulmonary disease remains unclear. PCR methods have shown an improved sensitivity in the detection of this fungus. It has been suggested that the PCR results be combined with another test such as IFA to create a diagnostic algorithm. METHODS: A multiplex nested-PCR procedure with a 16S rRNA gene as the internal amplification control was evaluated to determine the role of P. jirovecii in pulmonary disease. RESULTS: A 20% of the 199 bronchoalveolar lavage samples were PCR-positive, 13.5% samples were PCR-inhibited, and the rate of Pneumocystis-colonisation was 6.4%. The sensitivity, specificity, positive predictive value and negative predictive value of the nested-PCR were 100%, 93%, 70% and 100%, respectively. The sensitivity of the nested-PCR was higher than the current "gold standard" immunofluorescence assay (IFA) (p< 0.0001). PCR-negative and PCR-positive patients did not show any clinical or radiological differences in the medical variables studied. CONCLUSIONS: PCR could help the diagnosis of Pneumocystis pulmonary disease given the high negative predictive value of the technique. P. jirovecii DNA can frequently be detected in healthy population, so the analysis of the patient medical history is critical to make the correct clinical decision.