DNase use in the daily care of cystic fibrosis:: who benefits from it and to what extent?: Results of a cohort study of 199 patients in 13 centres

Short-term clinical trials with DNase have shown minor to moderate benefits in cystic fibrosis patients. This study was performed to analyse the effectiveness of DNase use in daily practice and to obtain information on its effects in the long term and at different disease stages. Patients being treated in 13 specialised units were included if they started DNase treatment before June 1996. Baseline data before DNase use and data during the DNase treatment period were recorded. Of the 199 patients included in the study 166 continued on DNase treatment while the data were being collected, The mean age (95% CI) was 14.5 (13.7; 15,2) years; 103 (51.8%) patients were female. The mean maximum change in forced expiratory volume in 1 s (FEV1) was observed during the first month of treatment [11.1% (6.1; 16.1)]. By the end of the first and the second year of treatment mean changes in FEV1 were 3.3% (-1.1; 7.6) and 5.1% (-0.7; 10.9) respectively; at the end of the same periods 34% of patients had improved their baseline FEV1 by 10% or more but in around 50% of patients the level fell below the baseline. A large inter-individual variability in changes in pulmonary function after the start of DNase treatment was documented. In addition, the medium-term response to treatment wets correlated with early response during the first 3 months. No consistent changes in exacerbation pattern were found during the first year of treatment. Conclusions The benefits of DNase use in daily practice are limited but apparently can be maintained in the medium term in some patients. A large inter-individual variability in response to DNase treatment has been documented and the benefits are doubtful in around 50% of patients. This observation points to the need to set up a withdrawal trial in these patients, using as an eligibility criterion the early response observed during the first 3 months of treatment.