Sessions

The aim of the present study was to determine the optimal sampling and sample-handling conditions required for the reliable measurement of serum ionized calcium concentration, to investigate the effect of storage time on ionized calcium concentration, and to evaluate its stability with respect to clinical relevance.

The study was conducted in two stages and included a total of 26 clinically healthy dogs. In the first stage, blood samples obtained from 14 dogs were used to investigate the stability of ionized calcium concentration under different preanalytical conditions. Serum samples were handled either aerobically or anaerobically and stored either at room temperature or under refrigerated conditions. Ionized calcium concentrations were measured upon arrival at the laboratory and at 24 and 48 hours after blood collection. Based on the results of this preliminary study, the second stage included an additional 12 dogs and focused exclusively on refrigerated samples to compare the effects of aerobic and anaerobic sample handling. Measurements were again performed upon arrival at the laboratory and after 24 and 48 hours of storage. Ionized calcium concentration measured in whole blood immediately after collection using a Siemens epoc blood gas analyzer served as the baseline value. Serum ionized calcium concentrations were measured at the Central Laboratory of the Department of Laboratory Medicine, Semmelweis University.

Taking into account both available analytical quality specifications and clinical relevance, the maximum acceptable deviation from ionized calcium concentrations measured using the blood gas analyzer was defined as 5% in the present study.

Ionized calcium concentrations showed a decreasing trend with increasing storage time. Compared with the baseline value, smaller deviations were observed in refrigerated samples than in samples stored at room temperature. Upon arrival at the laboratory and after 24 hours of storage, aerob and anaerob ionized calcium concentrations in refrigerated samples remained within the predefined acceptable range, whereas those in samples stored at room temperature were already outside this range. After 48 hours, the decrease exceeded the acceptable limit under all storage conditions. Overall, the mean deviation from the baseline value in refrigerated samples was −0.043 mmol/L under anaerobic and −0.048 mmol/L under aerobic conditions, compared with −0.075 mmol/L and −0.079 mmol/L, respectively, in samples stored at room temperature. Only minor differences were observed between aerobic and anaerobic sample handling.