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6-Minute Walk Distance (6MWD) Adjustment for Age/Sex in Pulmonary Hypertension Risk Calculator

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  • 6-Minute Walk Distance (6MWD) Adjustment for Age/Sex in Pulmonary Hypertension Risk: Explanation and Clinical Context
    The six-minute walk test (6MWT) measures the distance a patient can walk on a flat surface in six minutes (6MWD). In patients with pulmonary hypertension (PH) the 6MWD is a strong prognostic marker: shorter distances are associated with worse outcomes and higher mortality.
    However, because 6MWD is influenced by age, sex, height, weight (and hence by body size and anthropometry), adjusting the raw value by comparing it to a “predicted” distance based on healthy‐subject reference equations improves interpretability and allows more accurate risk stratification. For instance, using the sex-specific prediction equations by Enright P L & Sherrill D L (1998) gives a personalized expected 6MWD for comparison.
    In PH risk assessment guidelines, absolute 6MWD thresholds (e.g., <165 m, 165-440 m, >440 m) have been used to stratify patients, but a percentage of predicted value may better reflect functional impairment when adjusted for age/sex/size.
    Clinically, once you calculate the % predicted 6MWD, you can interpret: a % predicted well below normal (<50-70%) signals markedly reduced functional capacity, which in the PH context may warrant more intensive monitoring, consideration of advanced therapies, or referral to expert centre. A % predicted closer to or above ~80-100% suggests relatively preserved capacity and lower risk.

    Reference:
    Enright P L, Sherrill D L. Reference equations for the six-minute walk in healthy adults. Am J Respir Crit Care Med. 1998;158(5 Pt 1):1384-7. doi:10.1164/ajrccm.158.5.9710086.
    Lee WTN, Lau EM, Wong KW, et al. The role of percent predicted six-minute walk distance in pulmonary arterial hypertension. Eur Respir J. 2010;36(6):1294-1300. doi:10.1183/09031936.00012110.
    Costa GOS, et al. Prognostic value of six-minute walk distance at a South American pulmonary hypertension center. Pulm Circ. 2020;10(3):2045894020951384. doi:10.1177/2045894019888422.