Evaluation of predictive models for six minute walk test among children with pulmonary hypertension

Abstract

Background: Existing six minute walk distance (6MWD) prediction equations were developed using healthy children and include relatively small sample sizes. Children with congenital heart disease and pulmonary hypertension (PH) are often small-for-age, so the existing pediatric prediction equations are likely a poor fit for children with PH. Currently, there are no equations for 6MWD among children with PH.

Objectives: Evaluate the validity of five existing pediatric prediction equations among the 6MWD of children with PH, including for each World Health Organization (WHO) class. Develop a validated predictive equation for use in children with PH.

Methods/results: The 6MWDs from 711 six minute walk tests (6MWTs) of children aged four through 18years with PH were analyzed retrospectively and were evaluated against existing pediatric prediction equations. Existing pediatric prediction equations overestimated the walk distance among our population. The predicted distances versus actual distances were significantly different for each WHO class, with higher class associated with greater difference. A new prediction equation for 6MWD among children with PH was developed and validated with 65 additional 6MWTs. Our prediction equation demonstrates higher goodness of fit for all WHO classes than the preexisting pediatric equations.

Conclusions: Existing prediction equations for 6MWD among healthy children are not accurate for children with PH, particularly for children with more advanced stages of the disease (WHO classes III and IV). We present a new prediction equation for children with PH (WHO classes I through IV) that provides reference for medical care and management.

Keywords: Pediatrics; Pulmonary hypertension; Six-minute-walk test; Statistical model.