LAUSR

To the Editor We have taken interest in the study by Piotrowicz et al. [1] which was recently published in your journal. We congratulate the authors for having drawn attention to the evaluation of sarcopenia and also for the comparison with other diagnostic tests in sarcopenia. Although they declared that the study aimed to validate a Polish version of sarcopenia screening questionnaire SARC-F (Strength, Assistance in walking, Rising from a chair, Climbing stairs, and Falls) and to assess its clinical performance, we need to mention that there is confusion regarding the use of SARC-F for the evaluation of sarcopenia – i.e., due to its low sensitivity despite high specificity. Sarcopenia is defined as age-related loss of muscle mass and muscle function [2] and SARC-F is a self-reported “subjective” questionnaire to screen sarcopenia. It is noteworthy that an optimal screening test should be exquisitely sensitive in detecting the diseased subjects and specific in detecting the healthy subjects. Herewith, SARC-F mostly detects physically frail patients with mobility/activity limitation due to “severe sarcopenia” or other causes affecting the neuromotor control, i.e., movement/balance disorders, depression, polyneuropathy, cognitive impairment and pain [3]. Additionally, it may fail to catch the mild-to-moderate “real” sarcopenic patients. As such, without using prompt and objective muscle function measurements (i.e., grip strength and chair stand test (CST)), SARC-F would actually not be a valid tool to detect the real sarcopenic subjects. Since the authors already mentioned that it would be better to use SARC-F to rule out sarcopenia rather than case-finding, we believe that they would agree with us in this sense. Second, prevention of sarcopenia is easier and more important than its treatment. As mentioned earlier, detecting physically frail patients with SARC-F can inevitably result in missing the diagnosis of ‘real’ sarcopenic patients who should be managed earlier. On the other hand, the use of an objective test, i.e. grip strength (a simple, easy, and inexpensive screening tool), was shown to be a strong predictor of morbidity and mortality in all young, middle-aged and older adults [4]. In addition, as the anterior thigh muscle is the most commonly affected one with aging and as it is necessary for powerful mobility activities including standing, transfers and climbing, it is reasonable to measure the anterior thigh muscle function – i.e., CST or grip strength which is moderately correlated with the knee extensor strength [2, 3]. Herein, if measuring these objective parameters for muscle function are vital/sufficient for screening/diagnosing sarcopenia, frailty, disability, morbidity and even mortality, why is an additional/subjective test used in screening [4]? Last but not the least, we suggest to screen all middleaged and older adults (especially if they have renin–angiotensin system disorders) with basic functional tests (i.e. grip strength, CST for muscle function, and gait speed for poor outcome/severity) [3, 5]. If one subject has low muscle function (according to CST or grip strength), with a diagnosis of ‘probable sarcopenia’, we suggest to measure the anterior thigh muscle thickness (by ultrasound) either to detect sarcopenia (earlier) or to discriminate whether loss of muscle function (with/without mobility limitation) is caused by sarcopenia or by other causes affecting the neuromotor control as mentioned above [2, 3].