CORRELATION BETWEEN DIFFERENT TESTS TO ASSESS EXERCISE CAPACITY IN PATIENTS WITH CYSTIC FIBROSIS (CF)

Background: Regular assessment of exercise capacity in CF is a useful tool to facilitate exercise prescription and to monitor disease changes, in particular with aerobic tests that measure peak exercise (VO2). Indeed, aerobic fitness, measured by peak oxygen uptake during maximal exercise, is a strong predictor of survival. Aim: To investigate whether there were any correlations between the Cardio-Pulmonary Exercise Test (CPET), the Bruce Test (BT) and the Modified Shuttle Walking Test (MSWT). Methods: PATIENTS 18 CF patients (6 male, mean age 16 years, range 11-30), mean FEV1 80% predicted and mean VC 81% predicted. MEASURES All patients performed CPET on cycloergometer. All subjects performed BT that consisted of an incremental treadmill exercise test using Bruce protocol and with measurements of VO2. All patients performed MSWT in order to assess exercise tolerance, which was expressed in meters. A specific Armband was used for 3 days by each patient. A SenseWear®Armband is a complex multisensory activity monitor that includes a 2-axis accelerometer, sensor for heat flux, galvanic skin response, and skin temperature. Moreover it is able to calculate the metabolic equivalent (MET) and the number of steps/day. To evaluate physical activity expressed in METs/week, the Minnesota Leisure Time Activity Survey (MLTAS) Questionnaire, adapted form of the Minnesota Leisure Activity Survey, was used. Results:We found a significant correlation between CPET and BT (r =0,935, p<0,0001) and between CPET and MSWT (r = 0,731, p=0,0006). However there was no correlation between exercise performance indexes and pulmonary function and nutritional status parameters. Finally there was a significant correlation between CPET (expressed in VO2) and MLTAS (expressed in METs/week) (r=0,83, p<0,0001). Conclusions: Our data showed that BT and MSWT are feasible, cheap, and easy to perform. These tests may be a viable alternative to CPET for assessing exercise capacity in CF patients. Moreover, analysis of the questionnaire (MLTAS) showed that physical activity has a real physiological impact on performance index. Clinical Relevance Statement: BT and MSWT are a feasible and cheap alternative to CPET and they may be used routinely to assess exercise tolerance in CF patients. Monitoring physical activity should be a primary goal in CF care.