Anthropometric equations to estimate appendicular muscle mass from dual-energy X-ray absorptiometry (DXA): A scoping review.

BACKGROUND: Appendicular skeletal muscle mass (ASM) obtained from dual-energy x-ray absorptiometry (DXA) is recommended to quantify sarcopenia, but has limited availability in disadvantaged-income countries, moreover in an epidemiological context. Predictive equations are easier and less costly to apply, but a review of all available models is still lacking in the scientific literature. The objective of this work is to map, with a scoping review, the different proposed anthropometric equations to predict ASM measured by DXA. METHODS: Six databases were searched without restriction on publication date, idiom, and study type. A total of 2,958 studies were found, of which 39 were included. Eligibility criteria involved ASM measured by DXA, and equations proposed to predict ASM. RESULTS: predictive equations (n = 122) were gathered for 18 countries. The development phase involves sample size, coefficient of determination (r2), and a standard error of estimative (SEE) varying between 15 and 15,239 persons, 0.39 and 0.98, 0.07 and 3.38 kg, respectively. The validation phase involves a sample size, accuracy, and a SEE between 15 and 3,003 persons, 0.61 and 0.98, 0.09 and 3.65 kg, respectively. CONCLUSIONS: The different proposed predictive anthropometric equations of ASM DXA were mapped, including validated pre-existing equations, offering an easy-to-use referential article for clinical and research applications. It is necessary to propose more equations for other continents (Africa and Antarctica) and specific health-related conditions (e.g., diseases), once the equations can only have sufficient validity and accuracy to predict ASM generally when applied to the same population.

Cross-validation of 20 anthropometric prediction equations for appendicular muscle mass in older Brazilian women: a cross-sectional study / Validação cruzada de 20 equações antropométricas de massa muscular apendicular para idosas brasileiras: um estudo transversal

Objective: To test the cross-validation of anthropometric prediction equations for appendicular muscle mass (AMM) in older Brazilian women. Methods: Sixty-seven older women (69.84 ± 5.95 years old) underwent anthropometric measurements. AMM (kg) reference values obtained by dual-energy X-ray absorptiometry (AMMDXA) were compared to 20 anthropometric equations for estimating AMM in older adults. A paired t-test (p > 0.05), standard error of estimate (SEE < 3.50 kg), and r2 > 0.70 confirmed the validity of the equations. The agreement between predictions and the reference was also verified (Bland-Altman analysis of agreement between methods). Results: Four American equations and one Mexican equation were not statistically different from AMMDXA (p > 0.05) but did not present suitable r2 values for validation. The American equation from the National Health and Nutrition Examination Survey (NHANES), AMM (kg) = (-0.04 × age [years]) + (0.46 × calf circumference [cm]) + (0.32 × arm circumference [cm]) + (0.11 × thigh circumference [cm]) ­ (0.27 × body mass index [BMI, kg/m2 ]) + (0.07 × waist circumference [cm]) ­ 13 119 showed the best performance (r2 = 0.64; SEE = 3.24 kg), with minimal mean difference (0.26 kg), no heteroscedasticity for extreme values, and with high agreement with the Brazilian sample (-3.90 to 3.40 kg). Conclusion: When specific equations for a given population are not available, the use of generic equations of greater sample representativeness with scientifically and reliably analyzed data is allowed.

Objetivo: Testar a validação cruzada das equações antropométricas preditivas da massa muscular apendicular (MMA) em idosas brasileiras. Metodologia: Sessenta e sete idosas (69,84 ± 5,95 anos) foram submetidas a medidas antropométricas. Os valores de referência da MMA (kg) fornecida pela absorciometria de raios X de dupla energia (MMADXA) foi comparada com 20 equações antropométricas preditivas para estimar a MMA para idosos. Teste t pareado (p > 0,05), erro padrão de estimativa (EPE) < 3,50 kg e r2 > 0,70 confirmaram a validade das equações. A concordância entre as previsões e a referência também foi verificada (análise de concordância entre métodos de Bland-Altman). Resultados: Quatro equações americanas e uma equação mexicana não foram estatisticamente diferentes da MMADXA (p > 0,05), mas nenhuma delas apresentou r2 adequado para validação. A equação americana dos dados do National Health and Nutrition Examination Survey (NHANES), MMA (kg) = (-0,04 × idade [anos]) + (0,46 × circunferência da panturrilha [cm]) + (0,32 × circunferência do braço [cm]) + (0,11 × circunferência da coxa [cm]) ­ (0,27 × índice de massa corporal-IMC [kg/m2 ]) + (0,07 × circunferência da cintura [cm]) ­ 13,12 apresentou o melhor desempenho (r2 = 0,64; EPE = 3,24 kg): com diferença média mínima (0,26 kg), sem heterocedasticidade para valores extremos e alta concordância com a amostra brasileira (-3,90 a 3,40 kg). Conclusão: Quando não existem equações específicas para uma determinada população, é permitida a utilização de equações genéricas de maior representatividade amostral, cujos dados tenham sido analisados de forma científica e confiável