Reference equation for distance covered during the six-minute walk test in adults with acromegaly

Abstract

Introduction: Acromegaly is a multisystem pathology characterized by hypersecretion of GH and IGF-1 hormones. Cardiovascular, osteoarticular, muscle and respiratory disorders reduce exercise tolerance and functional capacity in these individuals. Clinically, this assessment can be evaluated through some submaximal field tests, with the six-minute walk test (6MWT) being the most clinically used in different populations. The determining factors to predict the distance covered in the 6MWT (6MWD), as well as reference equations for the test, are known in healthy adults and in some clinical conditions, but little is known about these factors in individuals with Acromegaly. Objective: The aim of this study was to evaluate the 6MWD in a sample of acromegalic patients, identify specific factors associated with 6MWD and develop a specific reference equation for this population. Methods and Results: Thirty-seven patients were evaluated, with a mean age of 49.05 ± 12.7 years, most of them female. All the patients underwent an anthropometric assessment, assessment of the strength of the palm pressure and the 6MWT. The mean 6MWD covered was 365.51 ± 65.09m, being considered low-low when compared to the predicted 6MWD values based on reference equations developed for healthy individuals. To find the variables that had the greatest impact on the 6MWD, we performed a multivariate logistic linear regression analysis, showing that the body mass index (BMI), age, sex and the dichotomous variable “gigantism” had the greatest influence. From this analysis, we obtained, from the non-standardized coefficients, the prediction formula for acromegalics: DPTC6, m = 770 + (-83.27 * sex) + (-2.11 * age) + (-8.10 * BMI) + ( -121.55 * gigantism), being: (Men = 0; Woman = 1) and Gigantism (Yes = 1 and No = 0). This analysis showed that the pore-prediction equation very sensitively translates the distance covered in the 6MWT in agromegalic patients with an R2 = 0.72 [CI95% 0.56 - 0.87, with a difference between the means of the distance walked < 1m and a standard error < 10m; p<.001. Conclusion: The reference equations developed to predict 6MWD overestimate the functional capacity in Acromegaly. The prediction of 6MWD through a specific equation in the future will be able to guide prognoses and evaluate treatment results in a more individual and assertive way.