Comparison of a fluorometric assay kit with high-performance liquid chromatography for the assessment of serum retinol concentration.

Background: Although high-performance liquid chromatography (HPLC) is the commonly used method for the analysis of retinol in biological samples, simple and rapid test kits are available.
Objectives: This study compared a rapid test kit (ICHECK Fluoro®) to HPLC for the assessment of serum retinol concentrations.
Methods: For the analysis by HPLC, sample preparation included standard deproteinization and extraction phases. The analysis by ICHECK was performed by injecting serum into IEX reagent vials (n=89) and mixing manually for separation. After precipitation of the proteins, the vial was introduced into the chamber of the ICHECK Fluoro and analysed at 0 min (ICHECK0min) and 15 min later (ICHECK15min). Bland and Altman approach was applied to test the agreement between HPLC and ICHECK.
Results: Mean HPLC, ICHECK0min and ICHECK15min values were 421.2±106.0 μg/L, 423.1±118.3 μg/L and 413.2±107.6 μg/L, respectively. Retinol concentrations significantly decreased in the IEX solution over time (p<0.001). No significant proportional bias was observed between HPLC and ICHECK0min (r-0.038, p=0.73) and ICHECK15min (r=- 0.024, p=0.82). Fixed biases (HPLC minus ICHECK) for ICHECK0min and ICHECK15min were respectively -1.9±23.1 μg/l (p=0.45) and 8.0±22.7 μg/l (p=0.002).
Conclusion: ICHECK Fluoro may offer a reliable mean for assessing serum retinol for measurements performed with no significant time delay.