Spirometry utilisation among Danish adults initiating medication targeting obstructive lung disease.

UNLABELLED This PhD thesis was written during my employment at the Research Unit of General Practice in Odense, University of Southern Denmark. It comprises an overview and three papers, all published or submitted for publication in international peer-reviewed scientific journals. BACKGROUND Non-infectious dyspnoea, chronic cough and wheezing are common symptoms in the population. Patients often present with these symptoms in general practice and have a high probability of having obstructive lung diseases. However, there is an indication that the majority of these patients are treated empirically with pharmacotherapy targeting obstructive lung disease and only few have additional tests conducted, although the predictive value of respiratory symptoms for diagnosing obstructive lung disease has proven to be low. Spirometry is recommended as the gold standard for confirming obstructive lung disease, and testing can also rule out airway obstruction in patients with respiratory symptoms caused by other illnesses, such as heart failure or lung cancer. Initiating medication for obstructive lung disease without spirometry entails the risk of these patients experiencing unnecessary delay in the diagnostic process and being exposed to unnecessary economic costs and medication risks. The literature has indicated that many users of medication targeting obstructive lung medication have not had spirometry performed and do not actually have obstructive lung disease. This potential quality gap needs to be assessed. Also, in order to target interventions enhancing earlier spirometry utilisation among patients initiating medication targeting obstructive lung disease, improved knowledge on patient and practice factors associated with spirometry testing is needed. AIMS Among first time users of obstructive lung medication we aimed: - To assess to what extent spirometry was performed within the first year of medication use (Study I) - To assess if patient characteristics like socioeconomic and demographic status were associated with spirometry testing (Studies I &II) - To assess if general practice characteristics were associated with spirometry testing (Study III) METHODS Register-based observational studies on first time users of medication targeting obstructive lung disease among adults over 18 years of age in 2008. The patient cohort was identified in the Danish National Prescription Register where all redeemed prescriptions for medication targeting obstructive lung disease are registered. All spirometry tests provided to the patient cohort in the time period 2007-2010 were extracted from the Danish National Health Service Register and the Danish National Patient Register and we assessed if patients had a spirometry registered in an 18- month time period counting from 6 months before to 12 months after their first redemption of medication. We linked socioeconomic and demographic patient variables and variables on practice characteristics from National registers to assess their association with patients having spirometry performed. RESULTS A total of 40,969 adults initiated medication targeting obstructive lung medication in 2008 in Denmark. The mean age of the cohort was 55.6 years (SD18.7) and approximately half of the mediations users had spirometry test performed. Initiating several types of medication targeting obstructive lung disease within the first year and redeeming medication repeatedly increased the odds of having spirometry performed. Women and patients in the oldest age categories had reduced odds of having spirometry performed. Being unemployed reduced the odds for spirometry testing among adults less than 65 years of age. Also, among the elderly (>65 years) living alone reduced the odds for spirometry testing; however this was only statistically significant among men. Some practice characteristics also influenced the odds for spirometry testing. Patients in partnership practices had higher odds for spirometry testing. Among singlehanded practices higher odds for spirometry testing was seen if practice had training practice status. We saw decreasing odds for spirometry testing with increasing age among doctors. CONCLUSION AND PERSPECTIVES This study has shown a lack of spirometry testing among patients initiating medication targeting obstructive lung disease. This underuse of spirometry testing indicates a quality gap and increased focus of spirometry utilization is needed when patients initiate medication targeting obstructive lung disease. The variation reported in spirometry testing across patient and practice characteristics was most predominant with regard to increasing age among patients and doctors, the remaining variables only account for small variations. However identification of these variations can help guide general practitioners to identify patients at increased risk of not having spirometry performed and help target future interventions for primary care.