Prognostic impact of plasma lipids in patients with lower respiratory tract infections - an observational study

A decrease in plasma lipids occurs during severe sepsis and has prognostic implications in critical illness. Whether lipids have prognostic implications or could help to differentiate community-acquired pneumonia from other lower respiratory tract infections remains unknown.

We analysed data from patients with lower respiratory tract infections enrolled in four prospective trials. We studied the time courses of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) and compared them with the underlying diagnosis and medical outcomes.

Of 572 patients included, 372 had community-acquired pneumonia and 200 acute and exacerbations of chronic obstructive bronchitis. We found significantly lower concentrations of TC, LDL-C and HDL-C in all patients on admission as compared to hospital discharge, particularly in community-acquired pneumonia. A multivariate logistic regression analysis including HDL-C, CRP, age and diabetes showed that HDL-C (OR: 0.18 [95%CI 0.11-0.3]) and CRP (OR: 1.01 [95%CI 1.01-1.02]) were independent predictors of community-acquired pneumonia. TC levels were significantly lower in non-survivors than in survivors (3.26 mmol/L [95%CI 2.58-3.96] vs 3.78 mmol/L [95%CI 3.01-4.65]). The prognostic accuracy, defined as the area under the receiver operator characteristic curve of TC to predict mortality, was 0.63 (95%CI 0.53-0.72) in all patients and increased to 0.94 (95%CI 0.86-1.00) in patients with bacteraemic community-acquired pneumonia.

In conclusion, low lipid levels, particularly low HDL-C, pointed to bacterial infection and low TC was predictive of adverse outcomes in patients with lower respiratory tract infections. Reflecting the severity of disease, plasma lipid levels may be a complementary tool in the diagnostic and prognostic workup of patients with lower respiratory tract infections.