Evaluation of i-STAT creatinine assay

Area of Science:

• Clinical Chemistry
• Point-of-Care Testing
• Analytical Chemistry

Background:

• The i-STAT analyzer is a validated point-of-care platform for various blood tests.
• A rapid, 2-minute blood creatinine assay has been developed for the i-STAT analyzer.

Purpose of the Study:

• To evaluate the performance of the new i-STAT creatinine assay.
• To assess the accuracy and precision of the i-STAT creatinine method compared to a laboratory-based method.

Main Methods:

• Imprecision was assessed through reproducibility studies using multiple solutions and repeats.
• Accuracy was determined by comparing i-STAT results with the Beckman Synchron CX7 method using 149 blood specimens.
• The impact of PCO2 variation on creatinine results was also investigated.

Main Results:

• Imprecision studies demonstrated excellent reproducibility with coefficients of variation (CVs) ranging from 0.4-3.4%.
• The i-STAT method showed high correlation (r=0.99) with the Beckman Synchron CX7, with a mean difference of 10.9%.
• Slightly higher i-STAT results were observed at lower creatinine concentrations (<100 micromol/l), suggesting a potential need to adjust the normal range upper limit.

Conclusions:

• The i-STAT creatinine assay is a simple, rapid, and precise method suitable for point-of-care use.
• Satisfactory accuracy was demonstrated, although a systematic bias towards higher results compared to the Beckman Synchron CX7 was noted.
• The PCO2 correction was not found necessary within the tested range (27-64 mm Hg).