Ao. Akanji, DIRECT METHOD FOR THE MEASUREMENT OF LOW-DENSITY-LIPOPROTEIN CHOLESTEROL LEVELS IN PATIENTS WITH CHRONIC RENAL-DISEASE - A COMPARATIVE-ASSESSMENT, Nephron, 79(2), 1998, pp. 154-161
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.