Establishment of an indocyanine green test using an automatic chemistry analyzer

The indocyanine green (ICG) clearance test has been used to assess the reserve of hepatic function. This method is based on the spectrometric measurement of its plasma concentration at maximum wavelength of 805 nm, which requires a spectrophotometer and associated maintenance. We established an ICG clearance test using a Toshiba 200FR automatic chemistry analyzer that can be tuned to a wavelength of approximately 805 nm. Five pooled sera spiked from 0 to 4.0 mg/dL were analyzed for linearity test and precision was determined at five levels in the range 0.1-2.0 mg/dL. The ICG retention rate at 15 min (R15) was determined for 38 patients using a conventional method and our method. The ICG clearance test using the automatic chemistry analyzer showed good linearity, and precision ranged from 0.3% to 1.0% for within-run CVs and from 0.6% to 4.7% for total CVs. The degree of agreement between the two methods was also acceptable (mean difference of 1.5%). It is expected that the ICG test using the automatic chemistry analyzer can replace the conventional ICG clearance test, considering the excellent agreement, good precision and linearity over a clinically relevant range.