UPLC-MS/MS analysis of keratan sulfate from urine samples collected on filter paper for monitoring and follow-up of Morquio A patients

Aim: Since 2014, enzyme replacement therapy (ERT) has been available for treatment of Morquio A syndrome. During clinical trials, urinary keratan sulfate (KS) has been a useful biomarker and showed a marked decrease in patients on ERT, demonstrating therapy efficacy. Unfortunately, quantitative urinary KS testing is not widely available in biochemical genetics laboratories for efficient monitoring and follow-up of treated patients. Materials & methods: A tandem mass spectrometry methodology was devised to analyze KS disaccharides and creatinine in urine specimens collected on filter paper. Results: All Morquio A patients presented abnormal results pretreatment compared with reference values. Conclusion: This collection procedure can be performed by patients at home and filter papers sent by regular mail to a specialized laboratory, facilitating follow-up of patients.