Resolving icteric interference by a novel photoisomerization device: Bilibox

Abstract

Icterus, a phenomenon caused by bilirubin elevation in the blood, is a common endogenous interference in chemistry testing, occurring either spectrally or through chemical reactivity with assay reagents. Often, laboratories have few options other than to dilute or reject samples exceeding icteric thresholds. However, recent studies have optimized in vitro photoisomerization of bilirubin to a 17-minute bilirubin half-life using 500 nm light at 37 °C. Using an enzymatic creatinine assay as a model, due to its prevalence in routine laboratory testing and susceptibility to icteric interference, our study explores the usage of in vitro photoisomerization by replicating these conditions in a device, the Bilibox, as means of resolving icterus in laboratory testing. Left-over icteric and non-icteric clinical samples, collected by lithium heparin vacutainer (n = 10), were analyzed for baseline creatinine, diluted creatinine (1:4 0.9 % NaCl), total bilirubin, direct bilirubin, and hemolysis, icterus and lipemia (HIL) indices. Samples were then placed in the Bilibox in two intervals of 30 min with repeat measurements of the aforementioned analytes. On average, icteric-index, total bilirubin (TBIL), and direct bilirubin (DBIL) decreased by 33.5, 39.1 and 39.9 % respectively following 30 min of Bilibox treatment; and by 47.6 %, 63.7 % and 59.8 % following 60 min. The average percent difference between the pre-exposure diluted and undiluted creatinine was 5.8 %, demonstrating the icterus interference. Following Bilibox treatment, the difference between undiluted (post-exposure) and diluted (pre-exposure) creatinine decreased to 0.02 % (p = 0.0232) and 2.2 % (p = 0.0021) at 30 and 60 min of treatment respectively, demonstrating resolution of interference. Consequently, photoisomerization can be utilized as an additional and reasonably quick method for resolving icterus when dilutional methods cannot be applied.