Rapid Aetiological Diagnosis of Pneumonia Based on Routine Laboratory Features

Abstract

The values of some basic laboratory features on admission to hospital were recorded and compared in 418 adult patients with community-acquired pneumonia, namely erythrocyte sedimentation rate, C-reactive protein, white blood cell (WBC) count, serum lactate dehydrogenase (S-LD), serum alanine-aminotransferase, and serum sodium. Discriminant analysis was performed to obtain an aetiological diagnosis. WBC value of > 15 × 10⁹/1 strongly indicated a bacterial and, especially a pneumococcal aetiology, whereas increased S-LD could imply a mycoplasmal infection. For patients <50 years of age the equation C₂ = −1.788+0.204 × WBC-0.0909 × S-LD was constructed, in which C₂>0 indicated a pneumococcal aetiology. This function correctly classified 31/33 (93.9%) patients with a mycoplasmal and 20/31 (64.5%) patients with a pneumococcal infection. Patients with viral, Haemophilus influence or chlamydial infection could not be discriminated from each other. The age of the patient, WBC and possibly S-LD on admission are easily accessible parameters and these results could therefore be of value in daily clinical practice in hospitals.