Measurement of plasma LDL cholesterol in patients with diabetes.
OBJECTIVE
To assess the accuracy of plasma LDL cholesterol concentrations estimated by the Friedewald formula and a direct immunoseparation method by comparison with a reference ultracentrifugation procedure in patients with diabetes.


METHODS
Fasting plasma samples with triglyceride concentrations < 4.5 mmol/l were collected from 100 patients with diabetes (28 type I and 72 type II) and LDL cholesterol concentrations were compared by the three methods.


RESULTS
LDL cholesterol values determined by the reference beta-quantitation procedure were highly correlated with both the Friedewald formula (r = 0.96) and a direct immunoseparation method (r = 0.92). Calculated (Friedewald) LDL cholesterol coincided with the reference method with < 10% error in 74% of the total diabetic group (82% of type I and 68% of type II diabetic patients). However, agreement between the direct LDL cholesterol and reference methods was significantly less (P = 0.02), with only 44% of patients having an error of < 10% (52% of type I and 41% of type II diabetic patients). The direct immunoseparation method for LDL cholesterol showed a positive bias with increasing triglyceride concentrations, particularly for patients with type II diabetes.


CONCLUSIONS
In the group of diabetic patients studied with plasma triglyceride concentrations < 4.5 mmol/l, the Friedewald formula provided an accurate estimation of LDL cholesterol. The direct immunoseparation method significantly overestimated LDL cholesterol at triglyceride levels between 2 and 4.5 mmol/l.
Whiting
M J
MJ
Department of Biochemistry and Chemical Pathology, Flinders Medical Centre, Bedford Park, South Australia. malcolm.whiting@flinders.edu.au
Shephard
M D
MD
Tallis
G A
GA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D008078:Cholesterol, LDL / Q000097:blood* / Q000302:isolation & purification; D003920:Diabetes Mellitus / Q000097:blood*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008863:Microspheres; D008875:Middle Aged; D011237:Predictive Value of Tests; D012044:Regression Analysis; D014280:Triglycerides / Q000097:blood*
D008078:Cholesterol, LDL; D014280:Triglycerides