eng Oriental Scientific Publishing Company Biomedical and Pharmacology Journal 0974-6242 2026-06-02 19 2 72048 article Iman Taj Elsir Ahmed 1 Mariam Abass Ibrahim 1 Sarah Osman 2 Alneil Hamza 2 Elyasa Elfaki 2 Department of Clinical Chemistry, Faculty of Medical Laboratory Science, Sudan University of Science and Technology, Khartoum, Sudan Department of Laboratory Sciences, College of Applied Medical Sciences, Jouf University, Alqurayyat, KSA An external quality assessment (EQA) is a fundamental tool for measuring the performance of laboratories based on standards and other labs. Poor quality of clinical labs can risk patient safety and the accuracy of clinical judgment. This research work aimed to evaluate the clinical chemistry laboratory in quality through EQA and Six Sigma in both public and private hospitals in Northern Sudan. This cross-sectional study in Dongola and Wadi Halfa, conducted between 2023 and 2024, involved 10 labs (3 public, 7 private) that were participating in an EQA program, using liquid-stable control sera at normal and abnormal levels. The selected analytes (glucose, urea, creatinine, and uric acid) were analyzed under routine conditions, using the respective lab's methods, instruments, and reagents. Performance evaluation was done through bias, coefficient of variation (CV), total error (TE), Z-scores, and Six Sigma. Total allowable error (TEa) was determined from Clinical Laboratory Improvement Amendments (CLIA) guidelines. Results indicated no significant differences between public and private labs concerning any of the analytes; however, both faced huge problems. Only one assay at the normal control level (uric acid from public labs, sigma=4) passed the standards, while others were below sigma=3. Moreover, at abnormal levels, none were at sigma-3. Quantitatively, mean bias ranged from -10.93% to +1.93%, CV from 2.28% to 29.13%, and total error from 9.82% to 37.83%, with the majority of analytes exceeding CLIA-defined TEa limits. Z-score analysis identified multiple outlier results. These findings indicate that clinical chemistry laboratory testing in Northern Sudan is in critical need of quality improvement. Urgent, structured interventions are recommended, including mandatory EQA participation, reinforcement of internal quality control practices, and targeted staff training programs. Future research should expand beyond this pilot to assess a broader range of analytes and laboratory phases, address pre- and post-analytical variables, and evaluate the impact of capacity-building and infrastructure interventions on overall laboratory quality. https://biomedpharmajournal.org/vol19no2/assessment-of-analytical-performance-in-clinical-chemistry-laboratories-of-public-and-private-hospitals-in-northern-sudan/ Clinical Chemistry External Quality Assessment Laboratory Performance Proficiency Testing Quality Control Sudan