Sarcopenia, being prevalent in up to 40% of older adults, is associated with adverse health outcomes. The international sarcopenia guidelines recommend screening for sarcopenia using the SARC-F. A previous meta-analysis (2017) reported poor validity of the SARC-F among community-dwelling older adults. Since then, modified SARC-F versions were developed and new sarcopenia definitions were published, including the SARC-F for case-finding. This systematic review and meta-analysis aimed to assess the reliability of the SARC-F and its concurrent validity to identify sarcopenia.

Systematic review and meta-analyses.

Adults (all ages) from any study population.

A systematic search was conducted in MEDLINE, EMBASE, Cochrane, and CINAHL (January 1, 2013, to April 6, 2020). Articles were included if they reported on the reliability and/or concurrent validity of the (modified) SARC-F. No restrictions were applied for sex, age, study population, or sarcopenia definition. Reliability measures included inter-rater reliability, test-retest reliability, and internal consistency. Meta-analyses were performed for concurrent validity.

The 29 included articles included 21,855 individuals (mean age of 63.3±14.6 years, 61.3% females) among community-dwelling (n = 16), geriatric inpatient (n = 5), geriatric outpatient (n = 2), nursing home (n = 2), and long-term care (n = 1) populations. The SARC-F had good (2/4 articles) to excellent (2/4 articles) inter-rater reliability, moderate (1/6 articles) to good (5/6 articles) test-retest reliability, and low (4/8 articles) to high (4/8 articles) internal consistency. The SARC-F had low to moderate sensitivity (28.9%-55.3%) and moderate to high specificity (68.9%-88.9%) according to the European Working Group on Sarcopenia in Older People (EWGSOP; n = 13), revised EWGSOP definition (EWGSOP2; n = 6), Asian Working Group for Sarcopenia (AWGS; n = 13), Foundation for the National Institutes of Health (FNIH; n = 8), International Working Group on Sarcopenia (IWGS; n = 9), and Society on Sarcopenia, Cachexia and Wasting Disorders (n = 2). The SARC-CalF had low to moderate sensitivity (45.9%-57.2%) and high specificity (87.7%-91.3%) according to the EWGSOP (n = 5), AWGS (n = 4), FNIH (n = 3), and IWGS (n = 3).

Despite the good reliability of the SARC-F, its low to moderate sensitivity and moderate to high specificity make it nonoptimal to use for sarcopenia screening. It is recommended to apply the diagnostic criteria for sarcopenia without screening.

Clinical and research interest in sarcopenia has burgeoned internationally, Asia included. The Asian Working Group for Sarcopenia (AWGS) 2014 consensus defined sarcopenia as "age-related loss of muscle mass, plus low muscle strength, and/or low physical performance" and specified cutoffs for each diagnostic component; research in Asia consequently flourished, prompting this update. AWGS 2019 retains the previous definition of sarcopenia but revises the diagnostic algorithm, protocols, and some criteria: low muscle strength is defined as handgrip strength <28 kg for men and <18 kg for women; criteria for low physical performance are 6-m walk <1.0 m/s, Short Physical Performance Battery score ≤9, or 5-time chair stand test ≥12 seconds. AWGS 2019 retains the original cutoffs for height-adjusted muscle mass: dual-energy X-ray absorptiometry, <7.0 kg/m2 in men and <5.4 kg/m2 in women; and bioimpedance, <7.0 kg/m2 in men and <5.7 kg/m2 in women. In addition, the AWGS 2019 update proposes separate algorithms for community vs hospital settings, which both begin by screening either calf circumference (<34 cm in men, <33 cm in women), SARC-F (≥4), or SARC-CalF (≥11), to facilitate earlier identification of people at risk for sarcopenia. Although skeletal muscle strength and mass are both still considered fundamental to a definitive clinical diagnosis, AWGS 2019 also introduces "possible sarcopenia," defined by either low muscle strength or low physical performance only, specifically for use in primary health care or community-based health promotion, to enable earlier lifestyle interventions. Although defining sarcopenia by body mass index-adjusted muscle mass instead of height-adjusted muscle mass may predict adverse outcomes better, more evidence is needed before changing current recommendations. Lifestyle interventions, especially exercise and nutritional supplementation, prevail as mainstays of treatment. Further research is needed to investigate potential long-term benefits of lifestyle interventions, nutritional supplements, or pharmacotherapy for sarcopenia in Asians.