BIOLOGICAL VARIATION OF SERUM-LIPIDS AND LIPOPROTEINS IN PATIENTS WITH CLINICALLY WELL-CONTROLLED NON-INSULIN-DEPENDENT DIABETES-MELLITUS

To investigate how the visit-to-visit variation in serum lipids measur ements affects the decision making concerning treatment according to t he National Cholesterol Education Program (NCEP) guidelines in patient s with clinically well controlled non-insulin-dependent diabetes melli tus (NIDDM) we have measured the biological variation (CVb) in serum t otal cholesterol (TC), triglycerides (TG), high density lipoprotein ch olesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C) in 2 6 patients with NIDDM. We found the CVb as follows: TC, 5.1%; TG, 17.0 %; HDL-C 4.4% and LDL-C, 8.3%. Confidence intervals (95%) were determi ned with total intra-individual variance values around the NCEP cut-of f points to evaluate how well one, two and three lipid measurements pr ovided reliable risk classification. A single TC measurements <177 mg/ dL or >263 mg/dL allowed confident classification as ''desirable'' or ''high risk'' respectively. For LDL-C, one measurement was accurate on ly at below 106.3 mg/dL or above 183.7 mg/dL. The average of three mea surements contracted these limits to <186.7 mg/dL and >253.3 mg/dL for TC, and <116.3 mg/dL and >173.7 mg/dL for LDL-C. For HDL-C also, mult iple measurements improved risk assignment in a similar fashion. There were no values which allowed assignment to the ''borderline high'' ca tegory with one TC measurement and with one and two LDL-C measurements . The mean of three TC and three LDL-C measurements allowed assignment to the ''borderline high'' category, if between 213.3 and 226.7 mg/dL for TC, 143.7 and 146.3 mg/dL for LDL-C. Seven patients (26.9%) in th is risk group based on the mean of two LDL-C estimates could be placed into a different category when the mean of three estimates was taken, even though the first two LDL-C test results did not differ by more t han 30 mg/dL. Our results suggest that repeated lipid measurement is i mportant especially for the ''borderline-high'' risk group because big variations existed in some patients, and further that TC is the most reliable quantity.