Abstract
Objectives To determine the performance of droplet digital polymerase chain reaction (ddPCR) assays in diagnosing Pneumocystis pneumonia (PCP), and to survey the sulfamethoxazole-trimethoprim (SMX-TMP) resistant mutations in our PCP cohort.Methods A prospective study was conducted from January 2017 to June 2018. Adult immunocompromised subjects with pneumonia were enrolled. Bronchoalveolar lavage fluid samples were obtained for standard microscopic testing and ddPCR to quantify the Pneumocystis MSG gene. DHPS and DHFR gene sequencings were performed to detect SMX-TMP resistance.Results Of 54 subjects, 12 had definite PCP, 7 had probable PCP, and 35 were non-PCP. In the PCP cohort, 10 (53%) had HIV infections. Using a cutoff value of ≥ 1.94 copies/µL, the ddPCR exhibited an overall sensitivity of 91.7% (61.5–99.8%) and specificity of 88.1% (74.4–96%). It showed a better performance when different cutoff values were used in subjects with HIV (≥ 1.80 copies/µL) and non-HIV (≥ 4.5 copies/µL). ROC curves demonstrated an AUC of 0.80 (95% CI, 0.56–1.0) for the HIV group, and 0.99 (95% CI, 0.95–1.0) for the non-HIV group. Of 16 PCP samples tested for DHPS- and DHFR-mutations, only DHPS mutations were detected (2). Most of the subjects, including those with DHPS mutations, demonstrated favorable outcomes.Conclusions The ddPCR exhibited a satisfactory diagnostic performance for PCP. Based on very limited data, the treatment outcomes of PCP did not seem to be affected by the DHPS mutations.
Highlights
Pneumocystis pneumonia (PCP) is a life-threatening opportunistic infection in immunodeficient individuals
The clinical characteristics of the 12 subjects with definite pneumocystis pneumonia (PCP) are summarized in Table 1, which compares the data for the subsets of people who were, and were not, human immunodeficiency virus (HIV) positive and those with a non-PCP diagnosis
Some of the subjects with a non-HIV immunodeficient condition had a history of using systemic corticosteroids (25%) or other immunosuppressive agents (50%) before developing PCP
Summary
Pneumocystis pneumonia (PCP) is a life-threatening opportunistic infection in immunodeficient individuals. The incidence of PCP in non-HIV immunodeficient individuals has been rising in recent years.[1] PCP remains a challenging conundrum in clinical practice. It has non-specific clinical manifestations and lacks a culture identification.[2] The mortality rate can reach 60% if diagnosis is delayed.[3] Standard PCP diagnostic testing comprises several microscopic methods.
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