The six-minute walk test: a guide to assessment for lung transplantation

A window of opportunity exists with regard to optimal timing for lung transplantation. Performance of a transplantation too early may rob the patient of months to years of survival, whereas waiting too long increases the risk of death before transplantation. Several studies have examined specific lung function tests as predictors of death, but none have been shown to be useful across the various disorders leading to end-stage lung disease. We therefore sought to examine the usefulness of the 6-minute walk test as a guide to assessment for transplantation.

We conducted a retrospective chart review of patients who were assessed and either were accepted or died waiting acceptance by the Toronto Lung Transplant Program between January 1991 and June 1995. One hundred forty-five patients with the following lung diseases were included: emphysema (n = 38), alpha-1-antitrypsin deficiency (n = 20), idiopathic pulmonary fibrosis (n = 26), primary pulmonary hypertension (n = 10), Eisenmenger's syndrome (n = 9), and cystic fibrosis (n = 41). The sensitivity, specificity, and positive and negative predicted values for a 6-minute walk distance of 300 and 400 m as a predictor of death were calculated.

Mortality rates were as follows: emphysema (7.9%), alpha-1-antitrypsin deficiency (15%), idiopathic pulmonary fibrosis (42.3%), primary pulmonary hypertension (50%), Eisenmenger's syndrome (11%), and cystic fibrosis (24.4%). A 6-minute walk distance of less than 400 m had the following characteristics for prediction of death: sensitivity 0.80, specificity 0.27, positive predictive value 0.27, and negative predictive value 0.91. Similar findings for a 6-minute walk distance of less than 300 m were as follows: 0.52, 0.80, 0.38, and 0.88, respectively.

The 6-minute walk test is a useful tool in the assessment of when to list patients for transplantation. A 6-minute walk test result of less than 400 meters appears to be a reasonable marker with regard to when a patient should be listed for transplantation.