Comments to “Rhabdomyolysis in the US Active Duty Army, 2004–2006”

Dear Editor-in-Chief: In their epidemiological report, “Rhabdomyolysis in the US Active Duty Army, 2004–2006,” Hill et al. (4) described the prevalence of rhabdomyolysis (RM) cases and their background characteristics. Although RM may be a final common outcome to various different diseases and injuries (e.g., trauma, exertion, hypoxia, infections, climatic injuries, metabolic and electrolyte disorders, and drugs [2]), Hill et al. defined medical encounters as RM if the International Classification of Diseases, Ninth Revision, code for RM, 728.88, appeared in any of the first four diagnostic positions of the encounter. This approach, which ignores the pathological causes to RM, makes the interpretation of the results problematic. We argue that when discussing the epidemiology of RM in young, active population such as soldiers, the differentiation between the exertional causes to the others is of a significant interest. The authors found higher risk to RM in African Americans, which they attributed to higher rates of sickle cell trait, but they did not mention whether the RM in African Americans was related to a codiagnosis of a sickle cell crisis, whereas the prevention of such a crisis has been previously discussed in the literature (3). The authors reported that age did not play a role in the epidemiology of overall RM. We argue that it is possible to assume that older individuals have more drug-induced RM compared with younger, more active individuals, which are expected to have higher prevalence of exertional RM. The authors did not refer to this important remark, which is highly important from an epidemiological point of view. The authors indicated a strong association between previous heat injury (HI) and the occurrence of RM (a 7- to 11-fold increased relative risk), but they did not report whether the occurrence of RM was part of a recurrent HI or a separate diagnosis. It has been shown that prior HI victims may be more prone to recurrent HI because of an acquired state of heat intolerance (1,5,8). Because no pathophysiological link has been described between prior HI and RM independent of HI, it can be assumed that RM cases in prior HI victims might actually have been the result of recurrent HI. Hill et al. did not refer to a codiagnosis of HI, a fact that may have a significant influence on the interpretation of the results. Moreover, it should be emphasized in this context that these recurrent HI may potentially be avoided by adhering to a return-to-duty protocol, such as the one applied by the Israeli defense force—using a heat tolerance test to evaluate the patients’ heat tolerance state and to safely return them to duty (6,7). Using this practical approach may also significantly reduce the number of restricted patients from active duty as presented by Hill et al. In conclusion, we suggest that describing the epidemiology of RM, especially in active duty army, should differentiate between the causes and risks to concentrate on proper diagnosis and prevention. The manuscript of Hill et al. lacks these data, which is a fact that may lead to inadequate interpretations of the results. Amit Druyan, MD Ran Yanovich, PhD Yuval Heled, PhD The IDF Institute of Military Physiology Heller Institute of Medical Research Sheba Medical Center Tel Hashomer, Israel