“…Some, such as that based on raised serum activity of pyruvate kinase, are at least potentially practicable,"7-'9 though having little or no advantage over creatine kinase. [20][21][22] Others, such as the tests based on abnormal polyribosomal protein synthesis of muscle in vitro,23 changes in phosphorylation of erythrocyte membrane spectrin 11,24 increased lactate dehydrogenase isoenzyme 5,25 and reduction in lymphocyte capping,26 are much more complex and still need validation. Electrocardiographic abnormalities,8 27 changes on quantitative electromyography,28-30 and pathological changes in the muscle under light3' 32 or electron microscopy3334 have also been used as supplementary tests for detecting carriers; and some authors have favoured combined tests.…”