Effects of posture on concentrations of blood constituents in healthy adults: practical application of blood specimen collection procedures recommended by the Scandinavian Committee on Reference Values.

Different procedures for the collection of blood for the determination of reference values in healthy adults have been subjected to practical testing. The Scandinavian Committee on Reference Values suggested that subjects lying in bed after an overnight sleep and ambulatory individuals, after 15 min of sitting in a chair, were two suitable and different reference populations. In forty subjects we found an increase from lying to sitting position of about 6.5% in the serum concentrations of proteins, enzymes and lipids. The corresponding increases for S-calcium and B-haemoglobin were approximately 3% whereas S-thyroxine, unexpectedly, changed by 11%. There were no significant changes of potassium and sodium values. For some constituents the changes were age and sex-dependent being greater in a group of elderly women as compared to a group of younger men. After 1 h of recumbency the concentrations of the constituents generally returned to those in the initial, lying position.