Creatine Kinase

• People with McArdle’s have raised CK / CPK. Baseline levels can be approx. 2,000–5,000 IU/L (normal values <190) [1] and can vary significantly with activity. With episodes of rhabdomyolysis CK can be much higher, even in excess of 100,000 IU/L.

• Establish a baseline level for patient by testing several times in the absence of recent injury.

• The results of CK tests following a series of injuries will assist the patient to understand how much damage they are doing. This will help them to manage their condition and avoid serious episodes.

• Set up a mechanism for the patient to be able to access immediate CK testing when they injure themselves. Abnormal results should be urgently communicated to the patient.

• CK tends to peak 24 hours after a McArdle injury, then falls by approx. 30% to 50% per 24 hours.

• Be wary of results that do not follow the above pattern, or that are reported as “above” a figure. This may indicate an error by the lab due to a result which is grossly outside the lab’s normal experience.

• An unusually high CK level after an injury may alert the patient to consider the need to go to the hospital. (See Medical emergencies, page 9.)

• A high CK need not indicate a cardiac event. If there is any concern, cardiac-specific proteins (e.g. Troponin I) give a clearer indication.

[1] See page 7, reference [3].