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

PRINCIPLES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.