Effects of infectious disease on plasma lipids and their diagnostic significance in critical illness

Background Plasma lipids can be affected by acute illnesses. The present study attempts to characterize the impact of infectious disease on plasma lipids in critical illness. It also aims to determine the value of plasma lipid routine measurements in the diagnosis of infection in critical illness in comparison to markers of infection and acute phase reactants. Materials and methods An observational study was carried out in 101 critically ill patients admitted consecutively to a medical intensive care unit in a university medical centre. Levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), and additional variables were measured in blood samples taken on the day of admission. Results In critically ill patients significantly lower levels of HDL-C and TC were found in infectious disease patients compared to non-infectious disease patients (P < 0.001). No significant differences in levels of TG were found between infectious and non-infectious disease patients. Using receiver operating characteristic (ROC) curve analysis, the area under the curve (AUC) value for HDL-C and TC in the diagnosis of infection was 0.791 (P < 0.001) and 0.730 (P < 0.001), respectively. At a cutoff value for HDL-C of <= 0.78 mmol L(-1), a sensitivity of 71.7% and a specificity of 86.0% were recorded. The AUC value of HDL-C was significantly (P < 0.001) inferior to procalcitonin (AUC: 0.967, P < 0.001) and non-significantly inferior to C-reactive protein (CRP) (AUC: 0.874, P < 0.001). HDL-C correlated with albumin (r = 0.7, P < 0.001) and CRP (r = -0.54, P < 0.001), but not with the Acute Physiology and Chronic Health Evaluation II score. There was no significant difference between the plasma lipid concentrations in survivors and non-survivors. Conclusions In critically ill infected patients, HDL-C and TC levels are lower than in non-infected critically ill patients. In this study the diagnostic accuracy of CRP is not better than the one of HDL-C. The diagnostic accuracy of procalcitonin is superior to HDL-C.