Sohrab Mansouri

Hydroxocobalamin and cyanocobalamin interference on co-oximetry based hemoglobin measurements

BACKGROUND Hydroxocobalamin (OHCbl) and cyanocobalamin (CNCbl) are dark-red colored analogs of vitamin B-12. OHCbl is used as an alternate antidote for cyanide poisoning. Due to the strong red color, if uncorrected, these cobalamins interfere with hemoglobin measurements and can introduce errors in spectrophotometric assay on co-oximeters. The impact of cobalamins on commonly used co-oximetry systems was compared to evaluate the accuracy of hemoglobin measurements and to further assess the ability of the instruments to detect and flag cobalamin interference. METHODS Blood samples spiked with varying concentrations of hydroxocobalamin or cyanocobalamin (0-2 g/l), were measured on 3 GEM Premier 4000 s, 3 IL 682 CO-Oximeter, 1 Radiometer ABL 735 and 1 Siemens Rapidpoint 405 analyzer. The effect of OHCbl or CNCbl interference on total hemoglobin and hemoglobin derivatives is evaluated using the measured difference between the control sample and the spiked sample. RESULTS Spectral measurements, blood measurements and delta spectral data confirmed that hemoglobin measurement accuracy is affected by the presence of OHCbl or CNCbl and that the source of interference is from errors in measurement algorithms, and not due to cobalamin induced hemoglobin changes. CONCLUSIONS Among the 4 co-oximeters tested in this evaluation, GEM Premier 4000 and Rapidpoint 405 analyzer showed minimal impact for hydroxocobalamin concentrations around 0.5 g/l. Cyanocobalamin displayed similar interference effect on co-oximetry measurements as OHCbl. The error detection system in the GEM Premier 4000 appropriately detected and flagged interferences on sample measurements.