Impact of posture on the "reference range" for serum proteins and calcium

The impact of water shifts due to changes in posture has been reinvestigated for serum protein and calcium concentrations in a young, healthy population. We found that generaly accepted normal ranges for total serum protein, and to a lesser degree for total serum calcium, are not acceptable as a reference range for a hospitalized population that is predominantly in a supine position. Our data indicate a smaller biological variability for total protein and calcium for a reference population in the recumbent posture as compared to the same population in the upright position.