Clinical testing means and methods

A method of determining approximate original ionized calcium concentration in serum taken from the body,

• said method comprising, equilibrating said serum sample with a first CO.sub.2 gas mixture and obtaining a first ionized calcium concentration at a first pH value of said serum,
• then equilibrating with a second CO.sub.2 gas mixture and obtaining a second ionized calcium concentration at a second pH value of said serum,
• plotting the points of said first and second obtained ionized calcium concentrations on a semi-log graph with log calcium concentration against pH and drawing a straight line therebetween,
• and selecting a specific predetermined average normal pH value on said line and obtaining an approximation of said original ionized calcium concentration.

A method of determining approximate original ionized calcium concentration in serum taken from the body,

• said method comprising,
• equilibrating said serum sample with a first known CO.sub.2 gas mixture to obtain a first arbitrary pH value,
• equilibrating said serum with a second CO.sub.2 gas mixture to obtain a second arbitrary pH value,
• plotting the logarithm of each CO.sub.2 partial pressure against the pH it produced on semi-log paper to produce first and second points,
• connecting the two points by a straight line and extrapolating from a specific predetermined average normal pH to determine the CO.sub.2 partial pressure required to produce an average normal pH,
• then using said specific CO.sub.2 partial pressure required to produce the specific predetermined average normal pH in the sample and directly measuring the ionized calcium concentration at said specific predetermined average normal pH.

A method of obtaining approximate original ionized calcium concentration in serum taken from the body, said method comprising,

• measuring the pH value and corresponding ionized calcium concentration value of a sample of said serum at a pH in the range of pH 7.1 to 7.75,
• plotting said value as a point on a semi-log graph of pH vs. log ionized calcium,
• producing a straight line through said point with said line having a slope corresponding to the average normal slope of ionized calcium concentration for body serum from average normal persons,
• and determining said approximate original ionized calcium concentration of said serum sample by reading from said graph at a predetermined pH value.

A method of determining original total calcium concentration in serum taken from the body after first determining ionized calcium concentration of said serum,

• said method comprising determining the volume (Vo) of a sample of said serum,
• determining the original ionized calcium concentration (Io) of said serum sample at a known pH,
• adding a known volume (Va) and known concentration (Ta) of calcium ions to said serum sample,
• again determining the ionized calcium concentration (If) of said serum at said known pH,
• and using the formula:
• ##EQU9## solving for said total original calcium concentration of said sample.

A method of simultaneously verifying calcium electrode repeatability and obtaining a calcium electrode serum calibration line by measurements on a single serum standard whose pH vs. ionized calcium relationship is known, said method comprising,

• forming a graph of log ionized calcium concentration on a vertical scale vs. pH on a bottom horizontal scale for said serum standard to produce a line A on said graph,
• adjusting the pH of said serum standard with CO.sub.2 gas and making pH and corresponding calcium electrode millivolts measurements at three different pH values.
• establishing a top horizontal millivoltage scale on said graph,
• and for each pH value at which a calcium millivolt reading is obtained plotting a point on said graph which point is determined by reading vertically up from said pH value on the bottom horizontal scale to the intersection with line A and then horizontally across to the corresponding calcium electrode millivolt value on the top horizontal millivolt scale to thereby obtain three points on said graph,
• and fitting a straight line B through said three points with the straightness of the line B being an indication of the repeatability and precision of the calcium electrode and the slope of line B, as expressed millivolts calcium electrode vs. log ionized calcium being the calcium electrode calibration line.

A method of producing a serum calcium standard of known ionized calcium concentration,

• said method comprising,
• selecting a normal serum sample with an ionized calcium concentration (Io) assigned an arbitrary value in the range of from about 4.0 to about 4.8 in mg% at a known pH value and a normal total calcium (To),
• measuring said total calcium concentration,
• adding calcium ions to said serum to change said ionized calcium concentration to a value (If) at said known pH and thus changing said total calcium (Tf),
• measuring said total calcium (Tf) after addition and determining said ionized calcium concentration If at said known pH by solving the following equation where only If is unknown:
• ##EQU10##

A testing apparatus for determining original ionized calcium concentration of serum taken from the body, said apparatus comprising

• a rotatable turntable,
• a plurality of serum sample containers mounted on said turntable and having upwardly facing container mouths,
• a cover positioned over said turntable to close said container mouths while permitting rotational movement with respect to said cover of said turntable along with said containers,
• means for rotating said turntable with respect to said cover at predetermined intervals to advance each of said containers to successive stations,
• means in said cover for passing a gas to a plurality of said containers at predetermined stations whereby the pH of said last-mentioned plurality of serum samples is simultaneously adjusted,
• a sampling tube mounted at one of said stations for withdrawing serum from a container at said one station.

A testing apparatus for determining pH dependent values of a body fluid, which apparatus comprises,

• a cover,
• a plurality of sample containers positioned below said cover and having upwardly facing container mouths mounted for sliding movement with respect to said cover,
• gas conduit means for passing a gas into said sample containers to actively mix said gas with liquid contents carried by said containers,
• and means for allowing escape of gas whereby gas flow from said gas conduit means and concurrent mixing are allowed.