<![CDATA[Internal quality control is an important process to ensure the quality of laboratory test results. Assayed serum control monitors examination accuracy and precision; however, room-temperature storage may affect analyte stability. This study aimed to determine how room-temperature storage duration affects the reliability of total bilirubin quality control. This experimental study used repeated measurements of normal and pathological serum samples at 0, 4, and 8 hours of storage. We evaluated results using the coefficient of variation (CV), bias, total error (TE), Levey-Jennings charts, and Westgard rules. Data were analyzed using Repeated Measures ANOVA. Results showed that storage duration significantly affected total bilirubin at the normal level (p=0.009) and the pathological level (p<0.001). All CV values met the acceptance criteria (<5%), and TE values remained below TEa. Levey-Jennings evaluation showed that quality control results remained within control limits at the normal level but were rejected (out of control) at the pathological level from 4 hours onward. Despite this loss of statistical control, total error remained below the allowable total error (TEa) threshold at both levels throughout the 8 hours, indicating that Westgard control status and total error assess different, complementary aspects of analytical quality. Storage duration affected total bilirubin quality control reliability, particularly at the pathological level, and acceptable storage duration should be judged by control level and QC criteria rather than a single uniform time limit.]]>
