<![CDATA[Background: The implementation of Internal Quality Control is crucial in clinical laboratories to ensure the accuracy and precision of test results, particularly for total bilirubin, which serves as an indicator of hepatobiliary disorders. Objective: This study aimed to analyze Internal Quality Control and sigma metrics for normal-level total bilirubin testing at a Type C hospital in Yogyakarta City by evaluating accuracy, precision, Levey-Jennings charts based on Westgard rules, and sigma metric values. Methods: This was a descriptive study with a quantitative approach utilizing secondary data from A total of 181 daily QC results from January–June 2025 were analyzed. Total sampling was employed. Data were processed using Microsoft Excel to calculate the mean, standard deviation (SD), Coefficient of Variation (CV%), bias (d%), and sigma metric values based on the 2024 CLIA Total Allowable Error (TEa) of 20%. Results: The Coefficient of Variation (CV%) values from January to June were 16.66%, 9.80%, 11.76%, 5.88%, 13.72%, and 10.78%, respectively. Only April met the precision criterion (CV ≤7%). Bias (d%) values were 8.62%, 9.80%, 8.82%, 10.59%, 11.76%, and 7.84%, respectively; all values fell below the Total Allowable Error (TEa) limit, indicating acceptable testing accuracy. Levey-Jennings charts revealed violations of the Westgard 1₂s rule from February to June and the 1₃s rule in May. Sigma metric values from January to June were 0.72, 1.04, 0.95, 1.56, 0.60, and 0.85, respectively. All results fell into the <3 sigma category. Conclusion: Total bilirubin testing demonstrated acceptable accuracy, yet precision was suboptimal. Evaluation of Levey-Jennings charts and sigma metric values indicates that the Internal Quality Control process requires improvement.]]>
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