Low density lipoprotein-cholesterol variability in patients with type 2 diabetes taking atorvastatin compared to simvastatin: justification for direct measurement?
OBJECTIVE
The benefit of direct, as opposed to calculated, low density lipoprotein -cholesterol (LDL-C) measurement remains unclear. This study compared the biological variability of direct LDL in patients with type 2 diabetes (T2DM) on equivalent doses of the short half-life statin, simvastatin or the longer half-life statin, atorvastatin.


METHODS
A cross-over study of biological variation of lipids in 26 patients with T2DM taking either simvastatin 40 mg (n = 10) or atorvastatin 10 mg. After 3 months on one statin, fasting lipids were measured on 10 occasions over a 5-week period. The same procedure was then followed on the other statin. The variability of LDL-C was established using a Beckman direct assay.


RESULTS
As a group, mean LDL was no different between statins (mean +/- s.d.) (1.69 +/- 0.60 mmol/l simvastatin vs. 1.67 +/- 0.60 mmol/l atorvastatin, p = 0.19). However, in all patients, the intraindividual biological variability of LDL while taking simvastatin was markedly higher than with atorvastatin (average s.d. = 0.17 mmol /l simvastatin vs. 0.01 mmol/l, p < 0.0001). Friedewald calculated LDL variability was no different between statins (average s.d. = 0.34 mmol /l simvastatin vs. 0.21 mmol/l atorvastatin, p = 0.19).


CONCLUSIONS
In contrast to calculated values, direct measurement revealed LDL to be much more stable (the s.d. being an order of magnitude) in T2DM patients taking atorvastatin rather than simvastatin. This means LDL targets can be consistently met with less lipid monitoring using atorvastatin rather than simvastatin. Direct LDL measurement may therefore have a particular role in monitoring patients on statin treatment.
Department of Diabetes, Endocrinology and Metabolism, Hull York Medical School, Hull, UK. tsathyapal@rediffmail.com
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Sathyapalan
S L
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Atkin
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Kilpatrick
D000368:Aged; D000704:Analysis of Variance; D000924:Anticholesteremic Agents / Q000627:therapeutic use*; D000069059:Atorvastatin; D008078:Cholesterol, LDL / Q000187:drug effects*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000188:drug therapy*; D003925:Diabetic Angiopathies / Q000188:drug therapy* / Q000517:prevention & control; D005260:Female; D006207:Half-Life; D006538:Heptanoic Acids / Q000627:therapeutic use*; D006801:Humans; D006937:Hypercholesterolemia / Q000150:complications / Q000188:drug therapy*; D050356:Lipid Metabolism / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D011758:Pyrroles / Q000627:therapeutic use*; D019821:Simvastatin / Q000627:therapeutic use*; D016896:Treatment Outcome
D000924:Anticholesteremic Agents; D008078:Cholesterol, LDL; D006538:Heptanoic Acids; D011758:Pyrroles; D000069059:Atorvastatin; D019821:Simvastatin