Continuous-flow enzymatic determination of high-density lipoprotein cholesterol

A simple, sensitive, and precise continuous-flow (Technicon Auto Analyser II (R) method using enzymic reagents to measure high-density lipoprotein (HDL) cholesterol in the supernatant of serum treated with heparin-manganese reagent is described. 1. The sensitivity of the system was improved by increasing the flow rates of both sample and re-sample manifold lines to 0.23 ml/min. This allowed a recorder full-scale deflection equivalent to 840 mg cholesterol per litre, and permitted a precise determination of cholesterol in the 200–600 mg/l range. 2. Interaction between Mn ++ and the enzymic reagents caused false elevations of the peak plateau on the chart readings, especially when 2M MnCl 2 was used. Addition of disodium ethylene-diaminetetra acetate (8 mmol/L) to the enzyme reagent eliminated the spike-like interference in the recorder tracings, and permitted more accurate chart readings. 3. The heparin-Mn ++ reagents contributed to the measured HDL-cholesterol. Use of a saline blank improved precision. 4. The inter-assay variation was determined by analysing (n = 26) 2 quality control serum pools: X 1 = 362 ± 11.5 mg/l (CV = 3.18%) and X 2 = 252 ± 14.4 mg/I (CV = 5.74%).