Table 2 Summary of diagnostic tests for LOPD

Creatine kinase

Varies from normal to 15 times the upper limit of normal

Alanine transaminase and aspartate transaminase

Frequently elevated

Forced vital capacity

Reduced in most patients. A drop of ≥10 % in supine versus upright is suggestive of diaphragmatic weakness and a drop >30 % is associated with severe diaphragmatic weakness

Electromyography

Myopathic EMG may be present, particularly in proximal muscles such as the paraspinal muscles. Myotonic discharges without clinical myotonia, fibrillation potentials, positive sharp waves, and complex repetitive discharges may also be seen

Dried blood spot

GAA activity reduced