Clinical Utilization of DiaSorin Molecular Polymerase Chain Reaction in Pneumocystis Pneumonia

Pneumocystis jirovecii polymerase chain reaction (PCR) testing is a sensitive diagnostic tool but does not distinguish infection from colonization. Cycle threshold (C_T) may correlate with fungal burden and could be considered in clinical decision making. Clinical use of PCR and significance of C_T values have not previously been examined with the DiaSorin Molecular platform.

Retrospective review of P jirovecii PCR, C_T values and clinical data from 18 months in a multihospital academic health system. The diagnostic performance of PCR with respect to pathology and correlation of C_T with severity were examined.

Ninety-nine of 1006 (9.8%) assays from 786 patients in 919 encounters were positive. Among 91 (9.9%) encounters in which P jirovecii pneumonia (PJP) was treated, 41 (45%) were influenced by positive PCR. Negative PCR influenced discontinuation of therapy in 35 cases. Sensitivity and specificity of PCR were 93% (95% CI, 68%-100%) and 94% (95% CI, 91%-96%) with respect to pathology. C_T values from deep respiratory specimens were significantly different among treated patients (P = .04) and those with positive pathology results (P < .0001) compared to patients not treated and those with negative pathology, respectively, and was highly predictive of positive pathology results (area under the curve = 0.92). No significant difference was observed in comparisons based on indicators of disease severity.

Pneumocystis jirovecii PCR was a highly impactful tool in the diagnosis and management of PJP, and use of C_T values may have value in the treatment decision process in select cases. Further investigation in a prospective manner is needed.