Two fluorimetric determinations of acid α-glucosidase activity in dried blood spot: Pompe disease in Iranian population

Abstract

Introduction: Pompe disease is a lysosomal storage disorder. This study aimed to validate and compare 2 fluorimetric methods for measuring α-glucosidase acid activity in dried blood spot sample (DBS), with potential applications in neonatal screening, and disease follow-up of Pompe patients among the Iranian population for the first time.

Materials and methods: The evaluation involved 3 enzyme levels and 7 parameters. The analysis included 141 Healthy individuals, 8 Pompe patients, and 10 obligate heterozygotes using reference and modified methods.

Results: Both methods exhibited highly linear calibration curves. The limit of detection (LOD) and limit of quantification (LOQ) were obtained in the micromolar concentration range in 2 methods. Inter-day and intra-day precision, expressed as relative standard deviations (RSD%) were calculated. The normal ranges were determined in healthy individuals. Receiver operating characteristic (ROC) curves were analyzed, and 2 parameters, total neutral α-glucosidase (NAG)/acid α-glucosidase (GAA) and pH ratio, were identified as cut-off values with excellent accuracy, sensitivity, and specificity for evaluating Pompe disease in both methods.

Conclusions: Establishing and implementing these 2 methods for the Iranian population effectively differentiated between healthy and patient individuals. Method II, with its shorter incubation time, demonstrated practicality in the clinical setting.

Keywords: Acid α-glucosidase; Dried blood spot sample (DBS); Fluorimetry; Glycogen storage disease type II; Iranian population; Pompe disease.