To the Editor:
In a recent article, Kaido et al. reported that sarcopenia was linked to increased posttransplant mortality in individuals undergoing living donor liver transplantation . The findings are considered highly important because accumulating knowledge on sarcopenia indicates that this condition may be associated with adverse outcomes in a wide range of clinical conditions, including posttransplant survival. However, we needed to point on some methodological issues regarding correct diagnosis of sarcopenia which is important particularly in clinical trials.
Multiple modalities are available to measure muscle mass. Magnetic resonance imaging and computed tomography are very precise imaging systems and the two gold standard techniques in this regard, however, high cost, limited access to equipment at some sites and concerns about radiation exposure with tomography limit their use . Dual energy X-ray absorptiometry (DXA) is another validated modality that can distinguish fat, bone mineral and lean tissues with lower radiation exposes . Although DXA costs relatively much lower, nonportability of the device stands as a major drawback in its availability. Noninvasive or less expensive tools have also been a focus of research, and bioelectrical impedance analysis (BIA) have emerged as an attractive tool to determine muscle mass. The theory of BIA measurement relies on V = pxI2/R equation wherein “V” is volume, “p” is resistivity, “l” is segment length, “R” is the segment resistance and weight, age and sex are incorporated into the estimation by multiple regression . Segmental BIA measures body in five segment (Vtotal = 2Varm + 2Vleg + Vtrunk) while nonsegmental BIA measures in a single segment (Vtotal = pxI2/R). BIA derived calculated through the equation introduced by Janssen et al. which relies on nonsegmental BIA derived R [Muscle mass = 0.401 × (height2/R) + (3.82 × gender − (0.071 × age) + 5.102] is another compelling tool to assess muscle mass .
Considering the current study, segmental BIA that was used to measure muscle mass may indeed not be appropriate for research purposes. As an example, segmental BIA underestimated muscle mass in a Japanese sample . Further, a recent study on segmental BIA measurement found that equations of the segmental BIA may not successfully represent the European population and should be revised. Although Pietrobelli et al. reported that segmental BIA can successfully be used to measure muscle mass, their hypothesis was tested in a small group of subjects and they used only DXA as the standard .
The European Working Group on Sarcopenia in Older People recommended use of presence of both low muscle mass + low muscle function (strength or performance) in the diagnosis of sarcopenia . The study by Kaido et al. assessed only muscle mass to define sarcopenia, therefore, some of their subjects could have been easily misclassified.
U. Safer1,*, I. Tasci1, V. Binay Safer2, and H. Doruk1
1Department of Geriatrics, Gulhane School of Medicine, Ankara, Turkey
2Department of Physical Medicine and Rehabilitation, Ankara Physical Medicine and Rehabilitation Research and Training Hospital, Ankara, Turkey
* Corresponding author: Umut Safer, email@example.com
The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation.