title: Effects of biological and analytical variations on the appropriate use of "reference intervals" in clinical chemistry. Proposal of a scheme for longitudinal assessment of laboratory values.
abstract: For twenty one different laboratory parameters the separate contributions of both biological (age, sex, hospitalisation) and analytical variations to the total variation have been examined. For each of the different laboratory parameters the reference interval and critical difference are given for the longitudinal evaluation of analysis results. These critical differences are not only calculated on the basis of the analytical imprecision from day to day, as has been usual until now, but the mean individual deviations of the reference samples have also been included. The critical differences given in this paper are therefore essentially higher for some parameters compared with the critical differences on the basis of the analytical deviation, and are therefore much more realistic quantities to be used for longitudinal evaluation. Finally for practical purposes a scheme is presented for use with longitudinal assessment of laboratory values, in order to enable the practising physician to consider these data in daily decision making.
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002648:Child; D002675:Child, Preschool; D019411:Clinical Laboratory Techniques / Q000592:standards*; D004573:Electrolytes / Q000097:blood; D004798:Enzymes / Q000097:blood; D005260:Female; D006801:Humans; D007223:Infant; D007501:Iron / Q000097:blood; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012737:Sex Factors
chemical_list: D004573:Electrolytes; D004798:Enzymes; D007501:Iron