COPD Overdiagnosis and Its Effect on 30-Day Hospital Readmission Rates

BACKGROUND: Although specific guidelines exist for diagnosing COPD on the basis of spirometry testing data (FEV₁/FVC < 0.70 or above the lower limit of normal), the literature suggests that overdiagnosis is common. Whether overdiagnosis increases 30-d readmission rates has not yet been explored. The objective of this study was to determine the prevalence of COPD overdiagnosis and its effect on 30-d hospital readmission rates in our institution.

METHODS: We retrospectively identified all subjects who were coded with a COPD hospital discharge in 2018 at Cleveland Clinic main campus and had spirometry data available, including FEV₁ and FVC. FEV₁/FVC was calculated and compared with the predicted lower limit of normal values. Hospital discharge diagnosis and 30-d hospital readmission data were captured along with comorbidities and other demographics.

RESULTS: In 2018, there were 424 hospital discharges with a COPD diagnosis with spirometry testing available. Of these subjects, 124 (29%) were overdiagnosed in the lower limit of normal group and 99 (23.3%) were in the ≥ 0.70 group. One hundred subjects (23.6%) had a 30-d hospital readmission. Of these subjects, 35 had FEV₁/FVC that was greater than their predicted lower limit of normal on spirometry. Of the 324 subjects who were not readmitted within 30 d, 89 (27.5%) had FEV₁/FVC greater than the lower limit of normal. If the 35 readmitted subjects had not been coded with COPD, the 30-d readmission rate would have decreased significantly from 23.6% to 16.7% (100 of 424 vs 65 of 389, P = .01). Even if all of the 124 subjects who had pulmonary function test data greater than the lower limit of normal had not been counted, the readmission rate would still have decreased from 23.6% to 21.7%, but this was not significant (from 100 of 424 to 65 of 300, P = .3).

CONCLUSIONS: COPD was overdiagnosed in our cohort of subjects; this was true whether the FEV₁/FVC < 0.70 standard or the lower limit of normal standard was used. Furthermore, this overdiagnosis artificially inflated the 30-d readmission rate. These results illustrate the caution providers should use when making a COPD diagnosis.