IS THE DETERMINATION OF LDL CHOLESTEROL ACCORDING TO FRIEDEWALD ACCURATE IN CAPD AND HD PATIENTS

Lipid abnormalities are a major cause of accelerated atherosclerosis i n patients with end-stage renal disease. In many clinical laboratories , the concentration of low density lipoproteins (LDL), the most athero genic lipoprotein fraction, is estimated by calculating LDL cholestero l according to Friedewald. Hypertriglyceridemia, a common finding in u remic patients, is a main limitation to the use of the Friedewald form ula, and the estimation of LDL cholesterol may, therefore, not be reli able in these patients. As accurate quantitation of LDL cholesterol is needed to decide on the initiation of lipid lowering therapy, we have evaluated the accuracy of the Friedewald formula in 171 patients on c ontinuous ambulatory peritoneal dialysis (CAPD), 136 hemodialysis (HD) patients and 887 clinically healthy individuals by comparing it with a combined ultracentrifugation and precipitation 'reference' method. W hen we excluded sera with total triglycerides above 400 mg/dl [4.56 mm ol/l], the Friedewald formula correlated excellently with the referenc e method; non-parametric correlation coefficients were 0.976, 0.971, a nd 0.956 in clinically healthy individuals, CAPD and HD patients, resp ectively. in the control individuals, the Friedewald formula produced slightly lower concentrations of LDL cholesterol than the reference me thod (means: 142 +/- 40 mg/dl vs 150 +/- 39 mg/dl or 3.68 +/- 1.04 mmo l/l vs. to 3.89 +/- 1.01 mmol/l, respectively). This was also true in HD patients (means: 145 +/- 51 vs. 146 +/- 49 mg/dl or 3.76 +/- 1.32 v s. 3.78 +/- 1.27 mmol/l, respectively), but not in CAPD patients (mean s: 165 +/- 50 vs. 162 +/- 47 mg/dl or 4.27 +/- 1.30 vs. 4.20 +/- 1.22 mmol/l). Our data show that, unlike in other forms of secondary dyslip oproteinemia, the Friedewald formula is sufficiently reliable in patie nts with end-stage renal disease. Much the same, however, as in contro l individuals, other methods to quantify LDL cholesterol like ultracen trifugation or lipoprotein electrophoresis are recommended when serum triglycerides exceed 400 mg/dl [4.56 mmol/l].