Cholesterol level in human serum: seasonal variations and differences in 14 distant regions.

To investigate differences between regions, a whole year's serum cholesterol results (304,156 data points) from 14 distant Polish laboratories (4,311 - 67,167 results) were used. The JEG, an original statistical method (http://ibib.waw.pl/JEGen.html) gives three levels of the Gaussian part of any analyzed dataset (Gaussian Reference Intervals, GRIs): low (GRImin), modal or middle (GRIopt), and high (GRImax). The quality was proven with reproducibility of 52 groups of week's sample collections in any laboratory; CV% was a mean of 5.73 and not worse than 8.29. The same groups were used to state the variation profiles for all three levels. The modal (GRIopt) serum cholesterol values were 4.73-5.72 mMol/L for women and 4.55-5.508 mMol/L for men. Sex and age dependency of the results were analyzed on 36-38 sets of 5-year age classes and showed, that there were more female results in childhood and in the older age classes, but in the youth age classes males dominated. The annual seasonal variation profile curves appeared as very variable, from M-letter forms through flat ones to W-letter forms. The shape of the variation curve was not stable in any particular laboratory and could vary from year to year to the opposite form. All results demonstrate the variability of cholesterol level in any analyzed subpopulation.