Using the hemolysis index of Abbott's Alinity c for the measurement of plasma free hemoglobin in ECMO patients

Objectives: Quantitative measurement of plasma free hemoglobin (fHb) concentrations is essential for monitoring pediatric ECMO patients, since hemolysis has a great impact on the patient's clinical outcome. The aim of this study was to validate the hemolysis index (HI) assay on Abbott's Alinity c system as a quantitative method to measure fHb. Methods: The performance of the HI assay, based on an automated spectrophotometric method recording the absorption at four different wavelength pairs, was evaluated using the 20 x 2 x 2 design according to the CLSIEP05-A3 guidelines. LLOQ and LLOD were calculated according to CLSI-EP17 guidelines with CVs set to 10% and 20%, respectively. Furthermore, the method was tested for interferences with bilirubin and Intralipid (R). Results: Linearity was ensured over an analytical measurement range of 30-7250 mg/L and the calculated LLOQ and LLOD were 80 mg/L and 50 mg/L, respectively. Intra-run and total imprecisions ranged from 0.9-3.4% and 1.0-3.4%, respectively. The HI assay correlated well with the Harboe method (HI (mg/L) = 0.998 * fHb (mg/L) + 28 mg/L, R = 0.998, n = 50) and interference testing showed no impact of bilirubin and Intralipid (R) up to 709 mg/L and 5580 mg/L, respectively. Conclusions: The HI assay on Abbott's Alinity c system allows a precise and accurate determination of fHb concentrations with no significant interferences in a simple, rapid and cost-effective way.