Objective: To evaluate the analytical and diagnostic challenges in interpreting the various organic acid results by gas-chromatography-mass spectrometry and to devise a protocol for analysis that is beneficial for prompt interpretation and diagnosis.
Study Design: Retrospective study.
Place and Duration of Study: Department of Chemical Pathology & Endocrinology, Armed Forces Institute of Pathology, Rawalpindi, from Apr 2015 to May 2017.
Material and Methods: We reviewed clinical data, biochemical investigations and urine organic acid profiles of 110 patients received for evaluation of a suspected organic acid disorder. Urine organic acid analysis was carried out by gas chromatography – mass spectrometry using Mass Hunter software.
Results: A total of 104 (99%) cases received were from the pediatric patients and 7 (6.3%) from adult patients. A total of 11 different organic acidurias were diagnosed. Other diseases (n=10) were also detected on the basis of their pathognomics metabolites and included tyrosinemia type 1 (n=4), alkaptonuria (n=5) and ornithine transcarbamoylase deficiency (n=1). Twenty-eight (25%) urine samples were either recalled or repeated for reasons like random urine sample yielding negative profiles in setting of a strong suspicion for organic aciduria (n=6), non-availability of clinical data (n=12) or delay in transportation >8 hours (n=10). Raised non-specific organic acid metabolites were seen in 23 (21%) cases. Lactic acid and ketones were detectable in 12 (11%) samples in the absence of raised plasma levels.
Conclusion: Urine OA profiles must be interpreted in context of complete clinical, nutritional and biochemical findings. Each laboratory equipped with this facility should devise their analytical protocols for meaningful interpretation of results.
Keywords : Gas chromatography-Mass spectrometry, Inherited metabolic disorders, Organic aciduria.