Long term follow up of changes in FEV1 and treatment intensity during Pseudomonas aeruginosa colonisation in patients with cystic fibrosis

Background-Colonisation with Pseudomonas aeruginosa (PA) is a striking feature of lung involvement in cystic fibrosis. To identify the clinical consequences of the different steps of colonisation with PA under a defined therapeutic regime (no prophylactic antibiotic treatment as long as patients had no severe pulmonary disease), their influence on pulmonary function and on therapeutic intensity was examined. Methods-Forty patients with cystic fibrosis were followed from first detection of PA (PA1), chronic PA colonisation (PAc), first mucoid PA detection (PAm), to chronic mucoid PA colonisation (PAcm). Percentage predicted forced expiratory volume in one second (FEV,), the number of intravenous antibiotic treatment courses, and the percentage of patients on inhaled antibiotics were followed retrospectively and longitudinally in relation to the different steps of PA colonisation. The annual changes in FEV, and therapeutic intensity in the two years preceding each step were compared with the two years following each step. Changes in FEV, were related to therapeutic intensity. Results-The mean (SD) annual changes in FEV1 (% predicted) worsened significantly only with the transition to the mucoid stages (PAm: 4.6 (13.2) versus -4.3 (8.1); PAcm: 7.3 (12.0) versus -4.8 (7.4)) with a mean difference (95% CI) between before and after the transition of 8.9 (2.6 to 15.2) for PAm and 12.1 (6.4 to 17.6) for PAcm. With non-mucoid PA stages the therapeutic intensity increased in the year of transition and with mucoid PA stages it increased in the years following transition. Therapeutic intensity was unrelated to changes in FEV,. Conclusion-With the treatment regime used an accelerated decrease in FEV, was successfully prevented in the non-mucoid stages but not in the mucoid stages of PA colonisation.