Testing and screening
When Pompe disease is suspected, confirmation of clinical diagnosis requires demonstration of the absence or significant reduction in acid α-glucosidase (GAA) enzyme activity.
This can be achieved by enzymology (to measure GAA activity), DNA testing (to determine GAA gene mutation) and histology/histochemistry (to measure lysosomal glycogen).1 Contemporary algorithms (Figure) aim to reduce diagnostic delay by first screening for GAA in dried blood spot (DBS) samples then following up positive results with GAA genetic analysis or GAA tissue assays.2
Diagnostic algorithm for late-onset Pompe disease.
Adapted from Toscano et al., 20132
(LOPD) Late-Onset Pompe Disease; (LGMD) Limb-Girdle Muscle Dystrophy; (EMG/NCS) electromyography and nerve conduction studies; (NMDs) neuromuscular disorders; (DBS) dried blood spot; (GAA) α-glucosidase A; *GAA activity <30%, borderline 30-40%.