How to check if it is pediatric rheumatic immune disease

Patient's question:

Creatine kinase 1275.3ul
Creatine kinase isoenzyme 24.1ul
Lactate dehydrogenase 345ul

Doctor's answer:

Hello: It may be necessary to perform an electromyogram or muscle biopsy to confirm whether you have polymyositis. The possibility of polymyositis is high. It is recommended to visit the rheumatology department of a regular hospital.