The following is a summary of “Interpretation of results of PCR and B-D-glucan for the diagnosis of Pneumocystis Jirovecii Pneumonia in immunocompromised adults with acute respiratory failure,” published in the July 2024 issue of Critical Care by Calvet et al.

The inherent properties and prevalence of the disease influence a diagnostic test’s accuracy.

Researchers conducted a retrospective study illustrating the probability of Pneumocystis Jirovecii Pneumonia (PJP) based on polymerase chain reaction (PCR) and Beta-D-Glucan (BDG) test results in patients with acute respiratory failure (ARF).

They gathered the diagnostic performance of PCR and BDG tests from existing literature. The incidence of PJP was evaluated in a dataset comprising 2,243 patients with non-HIV immunocompromised with ARF. A normal distribution was assumed across 5,000 random samples to simulate PJP incidence. Post-test probability was calculated using Bayes’ theorem.

The result showed that in patients with non-HIV with ARF, the incidence of PJP was found to be 4.1% (95% CI: 3.3–5.0). Supervised classification revealed 4 distinct subgroups with varying incidences, ranging from 2.0% (in the absence of ground-glass opacities,95% CI: 1.4–2.8) to 20.2% (among those undergoing hematopoietic cell transplantation, with ground-glass opacities and no PJP prophylaxis, 95% CI: 14.1–27.7). The overall population’s positive post-test probability was 32.9% (95% CI: 31.1–34.8) for PCR and 22.8% (95% CI: 21.5–24.3) for BDG. The negative post-test probability of being infected was 0.10% (95% CI: 0.09–0.11) for PCR and 0.23% (95% CI: 0.21–0.25) for BDG. In the highest-risk subgroup, the positive predictive value was 74.5% (95% CI: 72.0–76.7) for PCR and 63.8% (95% CI: 60.8–65.8) for BDG.

Investigators concluded that, despite high intrinsic performance, the low PJP incidence resulted in a low positive post-test probability and proposed a method to illustrate better pre- and post-test probabilities for improved diagnostic performance understanding.

Source: annalsofintensivecare.springeropen.com/articles/10.1186/s13613-024-01337-8