Use of the Friedewald Formula to Estimate LDL-Cholesterol in Patients with Chronic Renal Failure on Dialysis

Abstract

Increased plasma cholesterol, particularly that portion associated with LDL, is an established risk factor for coronary heart disease (1)(2). As a consequence, it is widely recommended (3) that LDL-cholesterol be determined in individuals with increased total cholesterol. Because isolation of the LDL fraction requires ultracentrifugation, a technique not generally available in service laboratories, the concentration of LDL-cholesterol is usually calculated by the formula of Friedewald et al. (4). The Friedewald formula provides an adequate estimate of LDL-cholesterol for most fasting specimens but is known to be less reliable as triglyceride concentration increases (5). Moreover, in patients with chronic renal failure, in whom an accumulation of remnant particles and increased concentrations of IDL-cholesterol have been found (6)(7), the estimate is possibly further compromised (8). Here we report results on specimens obtained from patients on dialysis with chronic renal failure that show no greater disparity between measured and estimated LDL-cholesterol concentrations than those seen in other patient groups in which the Friedewald formula is frequently used. Additionally we have reexamined the effect of IDL and VLDL composition on the reliability of estimations made with the formula. Two sets of blood specimens taken 6 months apart were obtained from 106 patients receiving hemodialysis or continual ambulatory peritoneal dialysis (9). Within this 6-month period, some patients received an inhibitor of hydroxymethylglutaryl-CoA reductase, some an inhibitor of angiotensin-converting enzyme, some both treatments, and some placebo only. Blood collected after an overnight fast and separated within 4 h provided serum specimens for analysis. Total …