DIRECT METHOD FOR THE MEASUREMENT OF LOW-DENSITY-LIPOPROTEIN CHOLESTEROL LEVELS IN PATIENTS WITH CHRONIC RENAL-DISEASE - A COMPARATIVE-ASSESSMENT

Background/Aim: This study was performed to comparatively evaluate the results obtained for low-density lipoprotein (LDL) cholesterol concen trations by either a newly described direct method or the Friedewald e quation in subjects with and without chronic renal disease. Methods: F asting plasma was obtained from a total of 169 subjects, 105 with norm al renal function (including 53 hyperlipidaemic) and 64 with chronic r enal disease (nephrotic syndrome and/or chronic renal failure; includi ng 40 hyperlipidaemic patients), and analyzed for LDL cholesterol usin g the Friedewald equation and a direct LDL assay method. Results: The Friedewald equation and the direct LDL cholesterol assay correlated we ll with each other (r = 0.79-0.90 in all subjects with plasma triglyce ride, TG, levels greater than or less than 4.0 mmol/l and with and wit hout chronic renal disease and/or hyperlipidaemia, all p < 0.0001). Th e values for LDL cholesterol, however, tended to be higher with the di rect measurement. This mean difference was trivial in hyperlipidaemic subjects with (8.5%) and without (7.1%) normal renal function (both p < 0.05), but could be clinically significant in those with TG > 4.0 mm ol/l (mean difference 18%, p < 0.001). Indeed, bias plots confirmed th is observation of wider negative bias for Friedewald estimation in the se moderately hypertriglyceridaemic subjects. Conclusion: For most rou tine laboratories the options immediately available for assessment of lipid levels are the Friedewald equation or the direct measurement. Th e Friedewald equation and the direct assay method for LDL cholesterol are about equally good for assessment of the LDL status in patients wi th chronic renal disease and plasma TG < 4.0 mmol/l. Where there are r estraints on laboratory budgets, it would appear appropriate that the more expensive direct assay method be restricted to cases in whom plas ma TG > 4.0 mmol/l or to patients who, for whatever reason, are unable to produce fasting samples.