The iStep Study: Development and Validation of an Incremental Exercise Step Test for Children With Cystic Fibrosis

Study Overview
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Brief Summary
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The progression of lung disease in cystic fibrosis (CF) results inevitably in a reduction in exercise capacity. The assessment of fitness and exercise capacity in CF is an important measure of the impact of the disease process, particularly if it is repeated over time. With recent advances in clinical management, CF lung disease in children can be relatively mild and exercise tolerance good. The currently available field tests e.g. 3 minute step test, are often completed too easily. These tests provide limited information relating to maximal exercise performance. By contrast, the maximal CardioPulmonary Exercise Test (CPET), a progressive, incremental, gold standard exercise test with breath by breath analysis of expired gas, has proved to be a valuable means of assessing exercise response in patients with CF. Its only limitation is the requirement for specialist laboratory facilities, equipment and staff. A new field test for evaluating exercise capacity in children is needed. This should be portable, easy to administer and simple to perform by young children, while providing a higher intensity of exercise which correlates with day to day activity patterns of children, and clinically relevant information in the short term and longitudinally. This test needs to be a good surrogate measure of exercise capacity when formal CPET is unable to be undertaken. By providing accurate and useful information the results can be used to prescribe and train individuals with CF safely and effectively and can also be used in the short and long term for guidance of the medical management of these complex patients. The aim of this study is to develop and validate the use of a new incremental step test to assess exercise tolerance/capacity in children with CF, compare this with the gold standard CPET and to provide normative healthy control comparison data The main objectives of the study are To develop an incremental step test to assess exercise tolerance / capacity in children with CF. To compare the incremental step test with the gold standard CPET To assess the level of exercise response produced by the incremental step test To assess the correlation between independent variables of lung function measurements, age, weight and height with VO2peak and other exercise test outcomes To assess the repeatability and evaluate the normal variability of the new incremental step test To provide healthy control normative data for comparison

Official Title
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The iStep Study: Development and Validation of an Incremental Exercise Step Test for Children With Cystic Fibrosis

Conditions
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Cystic Fibrosis

Intervention / Treatment
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* Other: iStep exercise test
* Other: CPET exercise test


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Clinical population inclusion Parental/guardian consent Participant assent Male or female Confirmed Cystic fibrosis diagnosis (by genetic genotype or positive sweat test) Receiving physiotherapy as part of their usual care Height >125cm to allow cycle ergometer use 6-16 years Healthy control population inclusion Parental/guardian consent Participant assent Male or female 6-16 years Exclusion Criteria: Clinical population exclusion <6 years and >16 years No consent / assent Frank haemoptysis in the last 48 hours Acute infective exacerbation (defined as increased temperature, additional antibiotics) Poor dietary intake/hydration Oxygen dependent at rest Arterial oxygen saturation (SaO2) <90% at rest Burkholderia cepacia Coexisting insulin dependent diabetes mellitus Methicillin-resistant Staphylococcus aureus (MRSA) positive Healthy control population exclusion <6 years and >16 years No consent / assent Acute infection (defined as increased temperature and antibiotics)

Ages Eligible for Study
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Minimum Age: 6 Years
Maximum Age: 16 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Cystic fibrosis<br>iStep exercise test CPET exercise test | Other: iStep exercise test<br>* newly developed submaximal exercise test<br>Other: CPET exercise test<br>* maximal gold standard exercise test<br>|
| Active Comparator: Healthy control<br>- iStep exercise test | Other: iStep exercise test<br>* newly developed submaximal exercise test<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Peak oxygen uptake (VO2peak) | Gold standard exercise test to determine peak oxygen uptake during exercise | Measured during the exercise test, day 1, maximum of 20 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Secondary breath by breath analysis outcome measures |  | Measured during the exercise test, day 1, maximum of 20 minutes | 
| Newly developed iStep exercise test outcome variables | Standard field exercise test outcomes of heart rate, oxygen saturations, time, level achieved, rate of perceived exertion, perceived breathlessness | Measured during the exercise test, day 1, maximum of 20 minutes | 
| Height, weight and body mass index measures | Height, weight and body mass index will be measured for descriptive purposes only | Measured at baseline on the day of testing, day 1, maximum of 5 minutes | 
| Reasons for termination of the incremental step test |  | Measured at the end of the exercise test, day 1, maximum of 5 minutes | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Exercise testing, Children, Exercise capacity