title: Long-term trends in biochemical data obtained from two population surveys.
abstract: A study has been made of the variations in monthly mean values of 10 serum constituents in subjects participating in two partly-concurrent long-term epidemiological surveys. Closely similar patterns of variation were found in men in both surveys and in men and women in one survey. During the 6 years of the study, four types of variation of the monthly mean concentrations were identified in varying combinations: abrupt changes of less than 2% not detected by quality control procedures; a gradual drift in mean value; haphazard variations in mean values; and seasonal variations in bilirubin and urea, identical in men and women. The implications of these findings for the design of long-term epidemiological surveys, and the criteria for designating variations as seasonal, are discussed.
mesh_terms: D000328:Adult; D001219:Aspartate Aminotransferases / Q000097:blood; D001663:Bilirubin / Q000097:blood; D001769:Blood / Q000378:metabolism*; D001774:Blood Chemical Analysis; D002118:Calcium / Q000097:blood; D002784:Cholesterol / Q000097:blood; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000097:blood; D011786:Quality Control; D012621:Seasons; D012709:Serum Albumin / Q000378:metabolism; D012964:Sodium / Q000097:blood; D014508:Urea / Q000097:blood; D014527:Uric Acid / Q000097:blood
chemical_list: D012709:Serum Albumin; D014527:Uric Acid; D014508:Urea; D002784:Cholesterol; D012964:Sodium; D003404:Creatinine; D001219:Aspartate Aminotransferases; D001663:Bilirubin; D011188:Potassium; D002118:Calcium