Diagnosis of mucopolysaccharidoses: how to avoid false positives and false negatives.

OBJECTIVE: This paper advocates a complete procedure, which includes both quantitative and qualitative analysis of urinary GAGs in the diagnosis of MPS in a clinically suspected population.

METHODS: Urine samples from 219 clinically suspected mucopolysaccharidoses (MPS) patients and 91 controls were analysed using a combination of methods. Quantitation of isolated urinary glycosaminoglycans (GAGs) were carried out using acid alcian blue complex formation method and qualitative urinary GAG analysis by multisolvent sequential thin layer chromatography

RESULTS: Of the 219 patients analysed, 131 were confirmed to be suffering from MPS. Quantitation of urinary GAGs alone would have missed 60 low GAG excreting MPS patients and misdiagnosed 26 high GAG excreting nonMPS as MPS patients. Further qualitative analysis and enzyme estimation were needed to identify these 60 low GAG excreting MPS patients and 26 high GAG excreting non MPS patients.

CONCLUSION: These results emphasize that quantitation of urinary GAGs alone cannot diagnose MPS patients, it should be coupled with qualitative analysis and enzyme estimations for differential/definitive diagnosis.