Analytical performances of the i-STAT portable clinical analyzer for the measurement of PO2 and PCO2

Aware of some limitations on blood gas results, we performed an extensive evaluation before introducing i-STATs in our hospitals. Three i-STATs were tested in parallel with an ABL-520, on three types of cartridges (EG7, EG6 and EG3), using tonometered whole blood (9 gas levels, n = 720) and aqueous QC solutions (3 levels, n = 600). Reference systems were the theoretical calculated values from gas composition used for tonometry and results given by the ABL-520, respectively. On aqueous controls dispersion intervals reached 10-20 mmHg for both analytes for inter-lot as well as intra-lot data. PO2 values on blood showed marked dispersion: 5 mmHg (CV = 2 to 7%) at clinically critical levels. PCO2 showed several (10%) major outliers: mV recording of the PCO2 electrode allowed to incriminate a pre-humidification problem (due to incorrect shipping conditions). Once outliers have been discarted, there still was a 5 mmHg non negligible residual dispersion (CV = 3 to 5%). i-STAT analytical performances for blood gases which are the analytes whose determination at the bed-side is potentially the most useful, do not match capabilities of classical laboratory instruments. Thus even though the i-STAT approach represents a seducive solution for the STAT problem, for the moment, it's use cannot be recommended in a hospital environment where classical instruments can be made available.