GALC and glycogen storage disease VI: There are two diagnostic tests commonly used when infants are referred to specialty care centers for confirmatory testing:Leukocyte GALC enzyme activity: When NYS began KD-NBS, leukocyte GALC activity, as performed in the Thomas Jefferson Lysosomal Diseases Testing Laboratory directed by Dr. David Wenger, was used as a confirmatory diagnostic assay and low GALC enzyme activity (previously set at ≤0.15 nmol/h/mg protein [2]), from this laboratory was thought to be predictive of who would develop IKD.