# Systemic inflammation, multi-organ injury, and acute kidney risk in psittacosis pneumonia: a biomarker-driven clinical characterization

## TL;DR

Psittacosis pneumonia causes severe inflammation and multi-organ damage, with a higher risk of acute kidney injury compared to typical pneumonia.

## Contribution

BAR and LDH are shown to be better predictors of acute kidney injury in psittacosis pneumonia than traditional markers.

## Key findings

- Psittacosis pneumonia is associated with higher rates of acute kidney injury compared to typical community-acquired pneumonia.
- BAR and LDH are strong independent predictors of acute kidney injury in psittacosis patients.
- Combining BAR and LDH improves the sensitivity and specificity for predicting acute kidney injury.

## Abstract

Psittacosis pneumonia, which is caused by Chlamydia psittaci, is a systemic inflammatory disease that often results in injury to multiple organs. Although liver and heart involvement are recognized, the incidence, risk factors, and predictors for acute kidney complications are not well known.

Our retrospective cohort study included 123 patients, comprising 47 individuals diagnosed with psittacosis pneumonia and 76 individuals with typical community-acquired pneumonia (CAP). These patients were admitted to Nanjing First Hospital, affiliated with Nanjing Medical University, between June 2019 and July 2024. The study conducted an analysis of clinical profiles, laboratory markers, and patient outcomes. The predictive efficacy of the Blood Urea Nitrogen to Albumin Ratio (BAR) and Lactate Dehydrogenase (LDH) in forecasting acute kidney injury (AKI) was assessed through the application of receiver operating characteristic (ROC) curve analysis.

In comparison to typical CAP, psittacosis pneumonia is characterized by markedly elevated systemic inflammation, as evidenced by increased levels of procalcitonin (PCT), C-reactive protein (CRP), and interleukin-6 (IL-6). Additionally, it presents with more severe lymphocytopenia, hypoalbuminemia, and extensive multi-organ damage, with a pronounced impact on hepatic and myocardial tissues. The incidence of AKI was significantly greater in the psittacosis group compared to the control group (34.0% versus 12.1%, P=0.003). In the psittacosis cohort, AKI demonstrated an independent association with increased levels of LDH (P = 0.01) and the BAR (P < 0.001), whereas no such association was observed with traditional inflammatory markers. The BAR (AUC = 0.88) and LDH (AUC = 0.79) demonstrated effective predictive capabilities for AKI, with their combined application enhancing sensitivity to 85.71% and specificity to 87.50%. The implementation of targeted therapy using omadacycline resulted in prompt clinical and biochemical improvements across all patients.

Psittacosis pneumonia constitutes a distinct systemic immuno-inflammatory syndrome that presents a significant risk for AKI. The composite biomarker BAR and the cellular injury marker LDH demonstrate superior predictive capabilities for AKI compared to traditional inflammatory indices, thereby providing accessible tools for early risk stratification. These findings emphasize the necessity of recognizing psittacosis as a unique clinical entity and advocate for vigilant monitoring of renal function in affected patients.