Rate of pulmonary function decline in South African children with cystic fibrosis

Background. Pulmonary function tests (PFTs) objectively measure the extent and progression of cystic fibrosis (CF) lung disease. The rate of lung function decline in developing countries has not previously been studied. Aim. To investigate the average annual rates of pulmonary function decline in South African children with CF from 1999 to 2006. Methodology: The medical records and best PFT over 3-monthly intervals of children attending the CF clinic at Red Cross War Memorial Children's Hospital, Cape Town, were retrospectively reviewed and analysed using the mixed model regression method. Results. A total of 1 139 PFT were recorded on 79 patients, with a median (interquartile range) of 14 (6 - 21) PFTs per patient. The mean (standard error) forced expiratory volume in 1 second (FEV1) at age 6 years was estimated at 73.83 (3.34) per cent predicted with an FEV1 decline of 0.23 (0.43)% per annum. FEV1 at age 6 was affected by age at CF diagnosis, genotype, and year of birth. Rate of FEV1 decline was significantly affected by Pseudomonas aeruginosa colonisation and genotype. Conclusions. Although FEV1 at age 6 years was low compared with developed countries, the annual rate of FEV1 decline in South African children with CF was minimal, setting the scene for improved survival in this population.