Missed diagnosis or misdiagnosis: how often do hospitalised patients with a diagnosis of chronic obstructive pulmonary disease have spirometry that supports the diagnosis?

Background Chronic obstructive pulmonary disease (COPD) is one of the most common clinical diagnoses among hospital inpatients. Diagnosis requires the demonstration of post-bronchodilator airflow obstruction. However, it is uncertain how often spirometry results are available at the time a diagnostic label of COPD is applied. Aims To identify how frequently spirometry results were available following an inpatient admission with a clinical diagnosis of COPD, and to determine how often the available spirometry results supported a clinical diagnosis of COPD. Inhaler prescription, at discharge, was also evaluated to determine one of the potential implications of diagnostic inaccuracy. Methods A single-centre retrospective observational study was undertaken at a 400-bed metropolitan health service between October 2016 and March 2018. Results A total of 2239 inpatient separations occurred in 1469 individuals who had a clinical diagnosis of COPD during the study. Spirometry results were not available in 43.6% (n = 641) of those with a diagnosis of COPD. A further 19.7% (n = 289) had spirometry results available at the time of admission that did not demonstrate fixed airflow obstruction. The available prescribing data (n = 443) demonstrated that inhaled medications were prescribed in a similar pattern, regardless of the availability of spirometry or whether the results supported a clinical diagnosis of COPD. Conclusions Inpatients with a clinical diagnosis of COPD frequently did not have supportive spirometry results that confirmed the diagnosis or had results inconsistent with COPD. Misdiagnosis and inappropriate prescribing require further attention to improve the quality of care in this setting.