Table 1. Diagnostic Determinations based on Confirmatory Testing Results.

“True positive” denotes all disease phenotypes, regardless of predicted severity or age of onset.

	Enzyme Activity	Mutation(s)	Biomarkers
True Positive	Within laboratory’s affected range	Known mutations or likely pathogenic alleles	Elevated GAGs (MPS1) or Glc4 (Pompe)
Not Affected	Low, but above laboratory’s affected range, or Within laboratory’s normal range	No mutations, or Carrier (one mutation plus wild type or pseudodeficiency allele) or Two pseudodeficiency alleles	Normal GAGS (MPS1) or Glc4 (Pompe)
Undetermined Disease Status	Low, but above laboratory’s affected range	Two variants of uncertain significance, or One variant of uncertain significance and one known or likely pathogenic allele	Normal GAGS (MPS1) or Glc4 (Pompe)