Nonadherence to Oral Linezolid After Hospitalization: A Retrospective Claims Analysis of the Incidence and Consequence of Claim Reversals

Background: Linezolid is available in an oral as well as an intravenous formulation. It is an oxazolidinone antibiotic and is effective in treating resistant gram-positive organisms such as methicillin-resistant Staphylococcus aureus and multidrug-resistant Streptococcus pneumoniae. Objectives: The goals of this study were to identify the incidence of claim reversals for oral linezolid in members who were recently discharged from a hospital and to study the subsequent pattern of health care utilization to quantify the consequences for members who have a reversed linezolid claim. Methods: This study was a retrospective claims analysis of Humana Medicare Advantage Prescription Drug patients who had a claim for oral linezolid after an inpatient discharge between April 1, 2006, and June 30, 2008. The incidence of reversed claims among those with a linezolid prescription was measured as a proxy for medication adherence. Propensity scores were calculated to account for differences in patients' propensity to have a reversed claim. The association of the claim reversal with subsequent expenditures was assessed through 3 multivariate regression models wherein the dependent variables were drug, medical, and total costs for the 60-day period after discharge. The key independent variable was the occurrence of a reversed linezolid claim, and control variables included the propensity score quartiles and other clinical and demographic characteristics. All costs were provided in US dollars and from the year in which they occurred. Results: Of 1046 patients identified (mean [SD] age, 69 [12] years; 51% male), 252 patients (24.1%) had a claim reversal for linezolid. Among these, 125 patients (49.6%) received linezolid within 10 days of the initial reversal, 39 patients (15.5%) received other antibiotics, and 88 patients (34.9%) did not receive any antibiotics. The unadjusted, mean outpatient drug costs were $696 and $2265 for patients with and without a reversal, respectively, whereas mean medical costs were $13,567 and $9355. Multivariable analyses revealed that members who did not receive linezolid after the claim reversal had significantly higher medical expenditures (Wald chi(2), 8.370; P = 0.004) and lower drug expenditures (Wald chi(2), 122.630; P < 0.01). The total costs did not differ significantly between the 2 groups (Wald chi(2), 1.540; P = 0.215), however, as the medical savings were partially negated by the higher drug costs. Conclusion: These patients with a reversed outpatient claim for linezolid had lower outpatient drug costs and higher medical costs in the 60-day period after the reversal. (Clin Ther. 2010;32:2246-2256) (C) 2010 Elsevier HS Journals, Inc.