To assess the reliability of iCheck Chroma to estimate retinyl palmitate and classify coconut oil as adequately fortified.
The test device (iCheck Chroma ; Bioanalyt Gmbh) which rapidly quantifies retinyl palmitate was tested against high-performance liquid chromatography (HPLC). Recovery, linearity and precision were measured at five target concentrations (5 to 25 mg Retinol Equivalents (RE)/kg). Agreement (Bland-Altman) was described and the diagnostic performance (sensitivity, specificity and predictive values) was calculated with HPLC as the gold standard.
Linearity ranged from 5 – 27.8 mg RE/kg and recovery was 84 – 130%. Precision ranged from 3.5% to 7.3% (intra-assay) and 1.3 to 14.7% (inter-assay). Mean difference was 1.9 mg RE / kg (SD 2.3; 95% CI 1.44, 2.37). Both methods classified 10 samples as unfortified or inadequately fortified. The specificity was 96% and the positive predictive value was 94% (IRR) and 100% for the IRR20. Sensitivity improved from 62% to 83% (IRR) and 93% to 98% (IRR20) subtracting the mean difference from iCheck reading.
The portable iCheck can be recommended for estimating vitamin A content in fortified coconut cooking oil in lieu of HPLC.