Elevated serum lactate dehydrogenase aids prediction of mortality in Pneumocystis jirovecii pneumonia without underlying human immunodeficiency virus infection – derivation of a clinical risk score

Pneumocystis jirovecii pneumonia (PCP) is associated with significant mortality amongst patients without underlying human immunodeficiency virus infection (HIV). We sought to develop a risk score to predict mortality in this population. We reviewed patients with a presumed or confirmed PCP and a negative HIV test from 2006-2023. We constructed a multivariable model to identify parameters independently associated with mortality and the adjusted odds ratios were converted to weights to derive a risk score. Subsequently, we compared the performance of our score to the CURB-65 score by means of area under receiver operating characteristic curve (AUC). In total, we examined 93 patients with PCP without HIV. Mortality was 31.2%. Risk factors for mortality included older age, male sex and high serum lactate dehydrogenase levels (LDH) and C-reactive protein levels. A risk score was derived comprising age>65 years (2 points), male sex (2 points) and LDH>770U/L (3 points). Our risk score (AUC 0.71, 95%CI 0.60-0.82) performed better than the CURB-65 score (AUC 0.53, 95%CI 0.41-0.66). A low-risk score of 0-1 had excellent negative predictive value for mortality (97.5%). In conclusion, a risk score comprising age, sex and LDH can predict mortality in PCP without underlying HIV and help with prognostication.