The basal metabolic ratio: A sensitive index for predicting early death after allogeneic stem cell transplantation
Authors: Satoshi Nishiwaki, Koichi Miyamura, Yoshihisa Kodera
Journal: American Journal of Hematology (2010)

Prof. Bech mentioned that the basal metabolic ratio (BMR), the new parameter we developed earlier [1], was proved to be linearly correlated to the ratio between the body masses only. However, he mistook our intended meaning, as suggested by his validation methodology. Older age at allogeneic stem cell transplantation (allo-SCT) is widely recognized as a risk factor for outcome. The novelty of BMR is to incorporate the factor of age into the concept of body mass. The figure of Prof. Bech consisted of patients all aged 50. Therefore it is not surprising that BMR was linearly correlated to the body mass ratio (body mass index (BMI) / 22). His verification lacked the element of age. We validated his point in our data set. We analyzed using three categories of the body mass ratio (A: BMI/22 ≤ 0.95; B: 0.95 < BMI/22 ≤ 1.05; C: 1.05 < BMI/22) instead of BMR. As for overall survival for 60 days after allo-SCT, the body mass ratio did not prove to be a significant risk factor in univariate analyses [A: Hazard ratio (HR) 1.75, 95% CI (0.86–3.60); P = 0.13; C: HR 1.58, 95% CI (0.72–3.45); P = 0.25 (vs. B)], indicating that BMR could be a more sensitive parameter in predicting early death after allo-SCT than body mass ratio. The relationship between BMR and age is shown in Fig. 1. The angle of the graph becomes sharper with age, indicating that the permissible body weight (0.95 < BMR ≤ 1.05) may be limited by age. The older patients become, the smaller the range of the permissible body weight becomes. Although the difference in the permissible body weight may be subtle, BMR could detect such differences and predict early deaths after allo-SCT. Relationship between basal metabolic ratio (BMR) and body weight. BMR varies according to age even with the same body weight and height. The angle of the graph becomes sharper with age, indicating that the older patients become, the smaller the range of the permissible body weight becomes. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] As early deaths after allo-SCT may be caused by complex factors, it is difficult to predict. Even though body mass was reported as an important factor, the predictive power might be insufficient [2]. Although age at allo-SCT is one of the classical risk factors, there was no clinical predictive index to combine body mass and age at allo-SCT. Basal metabolism varies according to body mass, sex, and age. The basal metabolism estimated by the Harris-Benedict equation [3] could reflect these factors. This is why we developed the BMR concept. And so far, we consider it to be one of the most sensitive predictive indexes for early death after allo-SCT compared with existing parameters, such as BMI, hematopoietic cell transplantation-specific comorbidity index [4], and performance status. We hope that the BMR will help to prevent unexpected early deaths after allo-SCT. Satoshi Nishiwaki*, Koichi Miyamura*, Yoshihisa Kodera*, * Department of Hematology, Japanese Red Cross Nagoya First Hospital Nagoya, Japan.