Clinical testing means and methods

Abstract

Clinical testing means for determining pH dependent body fluid substances. In vivo ionized calcium concentration is obtained by withdrawing a blood specimen, determining the pH of the serum when withdrawn from the body and later, determining the in vivo ionized calcium concentration at the original pH. The pH of the serum is adjusted to the original pH by equilibration with carbon dioxide after which the ionized calcium concentration is directly electrically measured. Alternately, the original ionized calcium concentration is extrapolated or interpolated by making two different pH adjustments, electrically measuring calcium ion concentration, graphing the points obtained on semi-log paper to form a straight line graph from which the original calcium ion concentration can be obtained knowing the original serum pH. In still another variation, an extrapolation can be made to determine the carbon dioxide adjustment required to produce the original pH, after which pH adjustment the original concentration can be directly measured. Other variations of the methods are used to obtain less reliable but useful ionized calcium concentrations. A relationship between ionized calcium and total calcium in serum is used to determine total calcium levels. Multiple sample serum testing means has a rotatable sample container turntable and a cover means through which carbon dioxide can be simultaneously introduced into plural samples. The sampling means carries pH determining means and ionized calcium determining means for rapid ionized calcium measurements.