Evaluating laboratory performance in external quality assessment schemes for urine organic acids by GCMS

Background: Biochemical genetics laboratory (BGL) differs from clinical chemistry laboratory in interpretation that is necessary to make its results meaningful. Aim: To evaluate the performance of BGL for analysis/interpretation of urinary organic acid (UOA) through external proficiency testing. Materials and Methods: BGL started participation in ERNDRIM since 2013 (18 samples from 3 surveys)and College of American Pathologist (CAP)(4 samples from 2 surveys) in 2014.Scoring/sample in ERNDRIMis on analytical and interpretative performance and recommendations for further testing (maximum score 4). Results: In ERNDIM, satisfactory diagnosis (score 4) was provided for 3-methyl crotonyl CoA-carboxylase enzyme deficiency, IVA, MMA, malonicacidurias, GAII, 3-MGA, L-Dopa agonist treatment, hyperphenylalaninemia, GAI and II, PPA and PKU. In a sample scored 3, majority participants were unable to associate a metabolite with diagnosis but weren’t penalized indicating educational role of ERNDRIM. Two samples misdiagnosed the disease. In one diagnosis of MSUD was missed due to mild excretion of metabolites and in another orotic acid peak wasn’t determined by GCMS. Both the samples were challenging and posed difficulties for laboratories. In CAP, GA I, neuroblastoma, PPA and PKU were correctly identified. Conclusion: Evaluation by CAP and ENDRIM has allowed BGL to monitor its performance and intensify their insight. Conducted by the Section of Chemical Pathology, Dept. of Pathology and Laboratory Medicine and Dept. of Pediatrics and Child Health*, Aga Khan University Hospital (AKUH). Pakista