Differentiating Chlamydia psittaci pneumonia from community-acquired pneumonia using clinical features and computed tomography findings

Chlamydia psittaci pneumonia (CPP) is a rare disease that is difficult to diagnose. Its clinical manifestations and chest imaging findings often overlap with those of other types of community-acquired pneumonia (CAP), and nonspecific treatment is likely to lead to rapid disease progression. This study aimed to explore the clinical and radiological differences between CPP and CAP. We enrolled 29 patients with non-severe CPP diagnosed using metagenomic next-generation sequencing, as well as 87 with CAP, who had been diagnosed between December 2019 and September 2023. The demographic, clinical, and radiological characteristics of CPP were analyzed and compared with those of CAP. Compared to the patients with CAP, those with non-severe CPP were more likely to experience fever ( P = 0.034), headache ( P = 0.009), asthenia ( P <0.001), abnormal auscultation of the lungs ( P = 0.020), and abnormal laboratory examination results—including lymphocyte count ( P = 0.002), C-reactive protein ( P = 0.001), aspartate aminotransferase ( P <0.001), alanine aminotransferase ( P <0.001), and creatine kinase levels ( P <0.001). Regarding radiological characteristics, CPP predominantly showed unilateral ( P = 0.003) and single-lobar ( P = 0.004) involvement, whereas CAP commonly exhibited bilateral and multi-lobar involvement. CPP was more likely to be associated with air bronchograms ( P = 0.026), interlobular septal thickening ( P = 0.001), and bronchovascular bundle thickening ( P <0.001) than CAP was. Clinical epidemiology, laboratory examination, and radiological characteristics are useful for diagnosing and differentiating CPP from CAP.