Yubi-Wakka Test for Sarcopenia Screening in the Community: Comparative Agreement, Diagnostic Performance and Validity with Calf Circumference Measurements.

Background: Screening tools such as calf circumference (CC) and Yubi-wakka (finger-ring) test have been recognized as effective tools by Asian Working Group for Sarcopenia 2019 (AWGS'19) for sarcopenia screening but their comparative agreement, diagnostic performance and validity are unclear.

Objectives: This study aims to determine: (i)agreement between calf and finger-ring circumference, (ii)diagnostic performance for low muscle mass and AWGS'19 sarcopenia diagnosis, (iii)correlation with muscle mass, strength, and physical performance, and (iv)association with frailty, life space mobility and physical activity.

Methods: We studied 187 healthy community-dwelling older adults (mean age=66.8+7.0years) from the GERILABS-2 study. CC was measured via (i) both calves in sitting and standing positions, and (ii) Yubi-wakka test by encircling the thickest part of the non-dominant calf with index fingers and thumbs of both hands. We performed Cohen's kappa to check for agreement, area under receiver operating characteristic curve (AUC) to compare diagnostic performance, partial correlations adjusted for age and gender to compare convergent validity, and logistic regression to determine predictive validity for outcome measures.

Results: Sarcopenia prevalence was 24.0% (AWGS'19). Yubi-wakka identified 16.6% of participants as screen-positive ("smaller"), showing moderate agreement only with non-dominant sitting CC measurements (k=0.421,p<0.001) and having lower diagnostic performance in determining low muscle mass (AUC=0.591 vs 0.855-0.870,p<0.001; sensitivity=57.1% vs 75.5-90.8%; specificity=58.4% vs 70.8-80.9%) and sarcopenia diagnosis (AUC=0.581 vs 0.788-0.818,p<0.001; sensitivity=55.6% vs 57.5-71.8%; specificity=74.4% vs 75.6-88.9%) compared to CC measurements. Yubi-wakka correlated significantly with muscle mass, grip strength and knee extension but not physical performance. When adjusted for age, gender and hypertension, Yubi-wakka was significantly associated with frailty (OR=3.96,95%CI:1.09-14.38), life space mobility (OR=2.38,95%CI:1.08-5.24) and physical activity (OR=2.50,95%CI:1.07-5.86).

Discussion and conclusions: Yubi-wakka provides a self-administered, low-cost and practicable community screening tool for sarcopenia. Our study affirmed the convergent and predictive validity of Yubi-wakka, albeit with lower sensitivity and specificity in diagnostic performance compared to CC measurements.