Lipid levels in Turkish population sinan tanyolac, Gladstone Institutes of Cardiovascular Disease, University of California, San Francisco, California, USA 22 May 2006 Dear Editor,I would like to congratulate authors of “Prevalence of metabolic syndrome-related disorders in a large adult population in Turkey’. This study was randomly selected in a large Turkish population. It has the potential to conclude the prevalence of metabolic syndrome in Turkish population. After I read this paper, I have several concerns about this study.1.) This study was done in 14 different centers. There was no mention of where the biochemical analysis had been performed. Did biochemical analysis perform in one center or different centers? Laboratory results can be variable if measurements were analyzed in different centers. Un-standardized data can cause errors in final analysis. 2.) It didn’t mention if there was any external standardization. External control of biochemical parameters is essential to perform this kind of population-based studies. Authors did not mention these topics in the method section. 3.) Blood samples were taken after 6 hours fasting. It is well known that lipid parameters, especially triglycerides levels show large variation if the duration of fasting is not long enough. Minimum of 12 hours fasting is usually required to determine correct lipid parameters. Fasting duration for sample collection is a crucial parameter to detect the metabolic syndrome. 4.) Other important concern is HDL cholesterol levels in Turkish population. Authors found that HDL cholesterol mean levels were similar in male and female subjects. It had been shown in several studies, i.e. in Turkish Heart Study (1) and Turkish Adult Risk Factor (2) study; Turkish women have ~7mg/dL higher HDL cholesterol level than Turkish men. I don’t know how can authors of this paper explain their findings? Reference:1. Mahley RW, Palaoglu KE, Atak Z, Dawson-Pepin J, Langlois AM, Cheung V, Onat H, Fulks P, Mahley LL, Vakar F, et al. Turkish Heart Study: lipids, lipoproteins, and apolipoproteins. J Lipid Res. 1995;36(4):839-59. 2. Onat A. Risk factors and cardiovascular disease in Turkey. Atherosclerosis. 2001;156(1):1-10. Review. Competing interests I have no competing interests.