Can the Roche hemolysis index be used for automated determination of cell-free hemoglobin? A comparison to photometric assays

Objectives: The aim of this study was to develop a novel method for automated quantification of cell-free hemoglobin (fHb) based on the HI (Roche Diagnostics).

Methods: The novel fHb method based on the HI was correlated with fHb measured using the triple wavelength methods of both Harboe [fHb, g/L = (0.915 * HI + 2.634)/100] and Fairbanks et al. [fHb, g/L = (0.917 * HI + 2.131)/100]. fHb concentrations were estimated from the HI using the Roche Modular automated platform in self-made and commercially available quality controls, as well as samples from a proficiency testing scheme (INSTAND). The fHb using Roche automated HI results were then compared to results obtained using the traditional spectrophotometric assays for one hundred plasma samples with varying degrees of hemolysis, lipemia and/or bilirubinemia.

Results: The novel method using automated HI quantification on the Roche Modular clinical chemistry platform correlated well with results using the classical methods in the 100 patient samples (Harboe: r = 0.9284; Fairbanks et al.: r = 0.9689) and recovery was good for self-made controls. However, commercially available quality controls showed poor recovery due to an unidentified matrix problem.

Conclusions: The novel method produced reliable determination of fHb in samples without interferences. However, poor recovery using commercially available fHb quality control samples currently greatly limits its usefulness.