Evaluation of the i-STAT analyzer for determination of ionized calcium concentrations in bovine blood.

BACKGROUND

Information regarding the performance of the i-STAT, a point-of-care analyzer, to determine ionized calcium (iCa ) concentration in bovine blood is limited.

OBJECTIVE

The primary goal of this study was to evaluate the agreement of the i-STAT against a traditional bench-top blood gas analyzer (Radiometer ABL800 FLEX) in the measurement of iCa in the blood of cattle with various disorders.

METHODS

In this study, 121 cattle with various diseases were used. Venous blood samples were run on the i-STAT and the Radiometer ABL800 FLEX for determination of blood iCa concentrations. Data were subjected to Passing-Bablok regression and Bland-Altman plots. The Radiometer ABL800 FLEX was the reference method and the i-STAT was the test method. The i-STAT performance was evaluated at two different cutoff values for iCa concentrations (<1.00 and <1.18 mmol/L) using the receiver operating characteristic curve.

RESULTS

The Passing-Bablok regression equation that fit the iCa concentration as measured with the i-STAT (Y) and the Radiometer ABL800 FLEX (X), was Y = -0.108276 [-0.15/-0.06] + 1.103448 [1.06/1.14] × X, with a residual deviation of 0.02. The deviation from the identity line was not significant (P = 0.64). The Bland-Altman difference plot revealed no bias between the i-STAT and the Radiometer ABL 800 FLEX. The i-STAT had a sensitivity of 100% (95% CI, 87.7-100.0) and 94.8% (95% CI, 87.2-98.6) at the iCa concentration cutoff values of <1.00 and <1.18 mmol/L, respectively.

CONCLUSIONS

iCa concentrations in bovine blood measured with the i-STAT agreed with those of the Radiometer ABL800 FLEX. In particular, the i-STAT predicted hypocalcemia with a high sensitivity.