Am. J. Respir. Crit. Care Med., Volume 165, Number 6, March 2002, 762-765

The Relationship between Genotype and Exercise Tolerance in Children with Cystic Fibrosis

HIRAN C. SELVADURAI, KAREN O. MCKAY, CAMERON J. BLIMKIE, PETER J. COOPER, CRAIG M. MELLIS, and PETER P. VAN ASPEREN

Children's Chest Research Centre; Department of Respiratory Medicine, Children's Hospital Institute of Sports Medicine, The Children's Hospital at Westmead (Royal Alexandra Hospital for Children); Department of Paediatrics and Child Health, University of Sydney, New South Wales, Australia; and Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada

The relationship between fitness and genotype in children with cystic fibrosis (CF) and at least one copy of the F508 mutation was examined. Genotype was classified according to the second CF mutation. Fitness was measured by peak aerobic capacity (using a modified Bruce protocol during treadmill exercise) and anaerobic power (using the Wingate test on a cycle ergometer). The class of cystic fibrosis transmembrane regulator proteins (CFTR) mutation was statistically related with aerobic capacity, peak anaerobic power, body mass index, lung function (forced expiratory volume in one second), and disease severity as measured by the Shwachman score. Patients with mutations causing defective CFTR production (Class I) or processing (Class II) had a significantly lower peak aerobic capacity (28.6 ± 4.2 ml/kg/min and 31.7 ± 5.4 ml/kg/min, respectively) than those with a mutation conferring defective regulation of CFTR (Class III) (43.9 ± 6.4 ml/kg/min). The peak anaerobic power in subjects with mutations inducing decreased CFTR conduction (Class IV) or CFTR mRNA (Class V), were significantly higher (11.4 ± 1.7 and 11.6 ± 1.5 watts/kg, respectively) than children with Class I (9.7 ± 1.4 watts/kg), Class II (9.8 ± 1.4 watts/kg), or Class III (10.5 ± 1.8 watts/kg) mutations. There were no statistically significant differences in the lung function of patients with the different mutations. These results indicate a relationship between CF genotype and some measures of fitness, the mechanisms of which remain to be determined.

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