Evaluation of a new method for determining the total calcium concentration using diluted plasma and an ion-selective electrode.
A newly developed method for determining the concentration of total calcium in plasma, using an ISE in diluted samples, was evaluated. This method is available on the CX3-Delta analyser (Beckman Instruments, Fullerton, CA, USA). Linearity, within-run imprecision and between-days imprecision were good. Inaccuracy was within appropriate limits. The correlation with results from atomic absorption spectrometry (AAS) was excellent. Reliable results were obtained in patients with hyper- and hypoproteinaemia, hypermagnesaemia and hyperphosphataemia. Citrate above 1 mmol/l caused a severe negative bias, so that citrate plasma cannot be used for calcium determinations with this method. The stability of the measuring system as well as the handling of the CX3-Delta were excellent. The preliminary reference interval for the concentration of total calcium determined with the present ISE method, using data from 124 healthy participants, was 2.18 to 2.51 mmol/l.
Boetefür
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Zentrallaboratorium des Allgemeinen Krankenhaus Altona, Hamburg, Germany.
Müller-Plathe
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D002118:Calcium / Q000097:blood*; D002951:Citrates / Q000494:pharmacology; D005069:Evaluation Studies as Topic; D006801:Humans; D017736:Ion-Selective Electrodes; D008274:Magnesium / Q000494:pharmacology; D012016:Reference Values; D013054:Spectrophotometry, Atomic
D002951:Citrates; D008274:Magnesium; D002118:Calcium