Impact of comorbidity on the risk and cost of hospitalization in HIV-infected patients: real-world data from Abruzzo Region

BACKGROUND: Due to the success of antiretroviral therapy, human immunodeficiency virus (HIV) infection has been transformed into a lifelong condition. In Italy, little is known about the impact of comorbidities (CMs) on the risk of hospitalization and related costs for people who live with HIV (PWLHIV). The objective of the study was to quantify the risk of hospitalization and costs associated with CMs in an Italian cohort of PWLHIV. METHODS: The study population included subjects aged ≥18 years with HIV infection, identified in the Abruzzo’s hospital discharge database among files stored from 2004 until 2013 and then followed up until December 2015. Patients’ CMs (Charlson Comorbidity Index [CCI)] were extracted from International Classification of Diseases, Ninth Revision, Clinical Modification codes in the hospital discharge abstracts. Poisson regression was used to compare the incidence rate of hospital admissions in patients with and without each CM class. Incidence rate ratios (IRRs) with 95% confidence intervals (CIs) were adjusted for age, sex and the other CMs. A generalized linear model under gamma distribution was used to estimate adjusted mean hospital costs. Costs were derived from official Italian Diagnosis-related group (DRG) based reimbursements. RESULTS: Among 1,026 HIV patients identified (mean age 47 years), 30% had at least one CM and 14.5% underwent hospital admission during the follow-up period. The risk of acute hospitalization significantly increased among patients with hepatitis C virus (HCV) coinfection (adjusted IRR 1.98; 95% CI: 1.59–2.47), renal (adjusted IRR 2.27; 95% CI: 1.45–3.56), liver (adjusted IRR 2.21; 1.57–3.13) and chronic pulmonary CMs (adjusted IRR 2.31; 1.63–3.32). Adjusted mean hospital costs were €2,494 in patients without CMs and €4,422 and €9,734 in those with CCI=1 or CCI ≥2, respectively. CONCLUSION: The presence of renal, liver and chronic pulmonary CMs, as well as HCV coinfection doubled the risk of hospitalization in the PWLHIV cohort. A CCI ≥2 is associated with a fourfold increase in hospitalization costs. Our study provides new evidence that CMs in PWLHIV increase the risk of hospitalization and local health service facilities.