<![CDATA[Quality assurance is a fundamental requirement for testing laboratories to demonstrate technical competence and ensure the reliability of analytical results. One important quality assurance mechanism is participation in interlaboratory comparison schemes or proficiency testing. This study had two objectives: 1. To evaluate the quality of drinking water from refillable drinking water depots (DAMIU) in Jambi, 2. to evaluate the analytical competence of the Integrated Laboratory Academic Service Unit (UPA LT) at the University of Jambi in measuring the concentrations of metals (Mn, Fe, Cu, Zn) and microbiological parameters (Escherichia coli and total coliforms) in drinking water from DAMIU through comparison with three laboratories accredited to ISO/IEC 17025:2017. Drinking water samples were collected from ten DAMIUs in the City of Jambi. Metal and microbiological analyses of each sample were carried out by 1. Jambi Provincial Environmental Laboratory (LP 413 IDN); 2. Jambi City Environmental Laboratory (LP 1194 IDN); 3. PT Jambi Lestari International (LP 1129 IDN), and 4. Integrated Laboratory of the University of Jambi (UPA LT). All DAMIU samples met the metal concentration standards, but only Kotabaru and Alam Barajo DAMIU samples met the microbiological criteria. Laboratory performance was evaluated using Z-score analysis. The analysis of Cu and Zn showed satisfactory performance across all participating laboratories (|Z| ≤ 2.0), indicating consistent measurement precision and accuracy. However, the determination of Fe and Mn showed questionable Z-scores (2.0 < |Z| < 3.0) in some laboratories, indicating the presence of systematic bias or inconsistencies in calibration that require corrective action through proficiency testing protocols. Microbiological analysis presented more significant analytical challenges, yielding unacceptable Z-values (|Z| ≥ 3.0) at DLH9, JLI12, and JLI15. The high prevalence of microbiological contamination in drinking water from DAMIU highlights a significant public health issue in the City of Jambi. Only 20% of DAMIUs in Jambi City meet the drinking water quality standards. Based on the interlaboratory comparison, UPALT is now eligible for an expansion of its testing scope to include metals and microbes in drinking water.]]>
