Is it necessary to adjust current creatine kinase reference ranges to reflect levels found in professional footballers?

Abstract

ObjectiveWe aimed to explore the validity of applying current reference ranges of the enzyme creatine kinase (CK) when analysing the medical status of professional footballers and to offer a more functional CK reference range for professional footballers.MethodsA sample of 27 professional male footballers competing in The Football League Championship was analysed. The single sample Wilcoxon signed-rank test was used to compare the CK distribution of the study group with that of a control group of military personnel reported in the literature.ResultsThe median values for study group and the published control group were 284 U/L and 124 U/L, respectively (P<0.001) suggesting that the average CK activity of professional footballers is higher than that of the normal healthy military population.ConclusionEthnicity, sex, age and physical exercise are factors that likely influence CK levels among various populations. From our analysis, we recommend a new 95% reference interval of 64.9 U/L to 1971.7 U/L for professional footballers.

The creatine kinase conundrum: a reappraisal of the association of isotretinoin, creatine kinase, and rhabdomyolysis

“…There are a multitude of factors that affect CK including: younger age, male sex, darker skin type, and prolonged, eccentric physical activity . Notably, an athlete can have a baseline average CK of 500–1,000 IU/l while long‐distance runners can have a CK 20 times normal 24 h post‐marathon . CK will rise to peak levels within 24–96 h and return to baseline within 4–10 days (half‐life of approximately 1.5 days) .…”

Reevaluation of Diagnostic Criteria for Exertional Rhabdomyolysis in Collegiate Wrestlers: A Case Series and Review

“…Due to the increased muscle mass, cases of rhabdomyolysis tend to affect more males than females [5,6,9]. Additionally, African Americans tend to have a greater occurrence when compared to Caucasians and those of South Asian descent [10]. Sickle cell trait, which effects African American males at a higher rate than other ethnicities, has been linked as a potential risk factor for rhabdomyolysis which may help explain this phenomenon [1,5,8].…”

“…Current laboratory ranges for CK/CPK levels fail to take into account gender, ethnicity, and activity level leaving physicians to use the same laboratory ranges for athletes, as they do for the general population likely leading to incorrect and misguided diagnosis [3,10]. The need for athlete specific references ranges led Mahmutyaziciouglu, et al [10] to propose a CK reference range for male professional footballers 64.9 U/L to 1971.7U/L [10].…”

“…Evidence of when renal damage occurs in relation to elevated CK/ CPK levels is not well understood further complicating the discussion. Mahmutyaziciouglu, et al [10] discussed that only CK/CPK values over 5,000 U/L should be concern for renal failure while other sources site levels of > 10,000 U/L as being diagnostic for ER [6,10]. With no definitive pathological value for CK/CPK, healthcare providers should be aware that levels of 20x the upper limit may be seen in those performing repetitive and strenuous exercise [5].…”

“…While the need for hospitalization and observation may be warranted, this decision is often derived from the physician's intuition and not based on laboratory findings alone [5]. It is imperative to understand that exercise can increase CK/CPK levels in the blood and that for the most accurate diagnosis, research needs to be conducted to establish sport specific reference ranges [10].…”