The Effect of Duration of Light Exposure at 1 to 6 Hour Intervals on Total Bilirubin Levels in Heparinizedized Plasma

Bilirubin is an important parameter in liver function testing that is strongly influ-enced by the quality of specimen handling during the pre-analytical stage. The pho-tolabile nature of bilirubin makes its levels susceptible to decline due to light expo-sure and delays in testing, which ultimately affects the accuracy of test results. This study aimed to analyze the effect of laboratory light exposure duration of 1, 2, 4, and 6 hours on total bilirubin levels in heparinized plasma at concentrations of 3, 5, and 10 mg/dL of bilirubin, and to compare these with samples covered using alu-minum foil. This study used a quasi-experimental design with a pretest-posttest non-randomized control group design and repeated measures. The samples con-sisted of pooled lithium heparinized plasma modified into icteric plasma with total bilirubin concentrations of 3, 5, and 10 mg/dL. Total bilirubin level testing was performed using the Dimethyl Sulfoxide (DMSO) method with a photometer, while data analysis included descriptive statistics, normality testing, and General Linear Model (GLM) Repeated Measures. The results showed that light exposure had a significant effect on total bilirubin levels in heparinized plasma starting from the first hour (p = 0.001) and continuing until the 6th hour (p = 0.000). Pairwise Com-parisons tests with Bonferroni correction showed that across all bilirubin concen-trations tested, light exposure caused a bigger decrease in bilirubin levels com-pared to samples protected with aluminum foil. From these results, it can be con-cluded that the longer the duration of light exposure and storage, the greater the decrease in total bilirubin levels in heparinized plasma, so and immediate testing and protecting specimens from light needs to be implemented to maintain the accu-racy of laboratory test results.