Comparison of Direct and Precipitation Methods for Estimation of Major Serum Lipoproteins in Hypertensive Patients

Abstract

Application of automated direct assays for analysis of high density lipoproteins cholesterol is increasing in response to the need by clinical laboratories to cope up with increasing workloads. However, performance characteristics of homogeneous assays often differ in important aspects from those of the earlier precipitation methods. Calculation of low density lipoprotein cholesterol (LDLC) by precipitation method is based on total cholesterol (TC), triglycerides (TG’s) and high density lipoproteins (HDLC) thus cumulatively carries errors of individual methods. Our study sought to compare the two methods. A total of 384 samples were collected in the medical outpatient clinic, analyzed in clinical chemistry section of Kenyatta National Hospital for TC, TG’s, HDLC, and LDLC by direct assays. HDLC and LDLC analyzed again by precipitation and Friedewalds formulae. The mean HDLC concentration by direct and precipitation methods was 1.52± 0.47mmol/L and 1.51 ± 0.47mmol/L respectively while those of direct and fridewald’s formulae for LDLC was 2.88 ± 1.01mmol/L and 2.89 ± 0.47 mmol/L respectively. There was no significant difference in mean for HDLC by precipitation and direct method at all total cholesterol ranges as well as Friedwalds formulae and direct method for LDLC at all triglyceride ranges p>0.05.Paired t test found no significant difference in the mean of HDLC estimated by direct analytical methods and precipitation method p=0.93. Average time for precipitation/calculated method was 45 minutes and direct was 20 minutes. There was no significant difference in LDLC estimated by direct analytical methods and Friedewald’s formulae p=0.91 both precipitation and precipitation/calculated methods gave similar results. Therefore, Selection should be based solely on workload, availability and technical expertise.