Evaluation of bilirubin concentration in hemolysed samples, is it really impossible? The altitude-curve cartography approach to interfered assays

BackgroundNeonatal jaundice might lead to severe clinical consequences. Measurement of bilirubin in samples is interfered by hemolysis. Over a method-depending cut-off value of measured hemolysis, bilirubin value is not accepted and a new sample is required for evaluation although this is not always possible, especially with newborns and cachectic oncological patients. When usage of different methods, less prone to interferences, is not feasible an alternative recovery method for analytical significance of rejected data might help clinicians to take appropriate decisions.MethodsWe studied the effects of hemolysis over total bilirubin measurement, comparing hemolysis-interfered bilirubin measurement with the non-interfered value. Interference curves were extrapolated over a wide range of bilirubin (0–30 mg/mL) and hemolysis (H Index 0–1100).ResultsInterference “altitude” curves were calculated and plotted. A bimodal acceptance table was calculated. Non-interfered bilirubin of given samples was calculated, by linear interpolation between the nearest lower and upper interference curves.ConclusionsRejection of interference-sensitive data from hemolysed samples for every method should be based not upon the interferent concentration but upon a more complex algorithm based upon the concentration-dependent bimodal interaction between the interfered analyte and the measured interferent.The altitude-curve cartography approach to interfered assays may help laboratories to build up their own method-dependent algorithm and to improve the trueness of their data by choosing a cut-off value different from the one (−10% interference) proposed by manufacturers.When re-sampling or an alternative method is not available the altitude-curve cartography approach might also represent an alternative recovery method for analytical significance of rejected data.