Risk factors for respiratory hospitalizations in a population of patients with a clinical diagnosis of COPD

Jovica Veljanovski,1 Daniel R Ouellette2 1Internal Medicine, Henry Ford Hospital, Detroit, MI, USA; 2Division of Pulmonary and Critical Care Medicine, Henry Ford Hospital, Detroit, MI, USA Purpose: The purpose of this study was to examine differences between patients clinically diagnosed with COPD with and without obstruction by spirometry and to identify risk factors for respiratory hospitalizations. Materials and methods: This is a retrospective analysis of all patients diagnosed with COPD at a large academic Internal Medicine Clinic in 2014, who had spirometry performed during the period 2013–2014. Two groups existed: one with obstruction termed classical COPD and another without obstruction. Demographics, comorbidities, prescribed medications, spirometry, respiratory hospitalization, and eosinophilia among other variables were compared between patients with and without obstruction. Risk factors for two or more respiratory hospitalizations during the period 2014–2015 were sought for both populations by both univariate and multivariate analyses. Subsequently, we studied the population without obstruction for risk factors for one or more respiratory hospitalizations first by univariate analysis and then by multivariate analysis. Results: Among 657 patients, 210 met inclusion criteria, with 157 having obstruction on spirometry and 53 without obstruction. There was no difference between those with and without obstruction on the rate of respiratory hospitalization when using two or more respiratory hospitalizations (p=0.397) or one or more respiratory hospitalizations (p=0.467). Nontreatment risk factors associated with two or more respiratory hospitalizations by multivariate analysis included a maximum eosinophil count above the threshold of 0.5 K/µL (maximum eosinophil number threshold [MENT]; p=0.001, OR =3.792, 95% CI =1.676–8.582) and % predicted forced expiratory volume in the first second (p=0.031, OR =0.978, 95% CI =0.959–0.998). In patients without obstruction, MENT above the threshold of 0.5 K/µL (p=0.032, OR =5.087, 95% CI =1.147–22.557) was the only risk factor associated with one or more respiratory hospitalizations. Conclusion: In a clinically diagnosed COPD population who had spirometry performed, the presence of airflow obstruction was not a risk factor for respiratory hospitalizations. The most significantly associated nontreatment factor associated with respiratory hospitalization, both in the study population as a whole and in the cohort without obstruction, was MENT above the threshold of 0.5 K/µL. Keywords: chronic obstructive pulmonary disease, airflow obstruction, spirometry, eosinophili