Outpatient Treatment of Deep Vein Thrombosis in the United States: The Reasons for Geographic and Racial Differences in Stroke Study
BACKGROUND: Outpatient versus inpatient treatment of deep vein thrombosis (DVT) is believed to result in equivalent outcomes with decreased costs. Little is known about the adoption of outpatient DVT treatment in the United States.
OBJECTIVE: To describe the uptake of outpatient DVT treatment in the United States and understand how comorbidities and socioeconomic conditions impact the decision to treat as an outpatient.
DESIGN AND SETTING: The Reasons for Geographic and Racial Differences in Stroke cohort study recruited 30,329 participants between 2003 and 2007. DVT events were ascertained through 2011.
MEASUREMENTS: Multivariable logistic regression was used to determine the correlates of outpatient treatment of DVT accounting for age, sex, race, education, income, urban or rural residence, and region of residence.
RESULTS: Of 379 venous thromboembolism events, 141 participants had a DVT without diagnosed pulmonary embolism and that did not occur during hospitalization. Overall, 28% (39 of 141) of participants with DVT were treated as outpatients. In a multivariable model, the odds ratio for outpatient versus inpatient DVT treatment was 4.16 (95% confidence interval [CI], 1.25-13.79) for urban versus rural dwellers, 3.29 (95% CI, 1.30-8.30) for white versus black patients, 2.41 (95% CI, 1.06-5.47) for women versus men, and 1.90 (95% CI, 1.19-3.02) for every 10 years younger in age. Living outside the southeastern United States and having higher education and income were not statistically significantly associated with outpatient treatment.
CONCLUSIONS: Despite known safety and efficacy, only 28% of participants with DVT received outpatient treatment. This study highlights populations in which efforts could be made to reduce hospital admissions.
© 2017 Society of Hospital Medicine
Outpatient treatment was defined as receiving a DVT diagnosis in an emergency department or ambulatory clinic but not receiving an overnight hospitalization. Inpatient treatment was defined as at least 1 overnight stay in a hospital (but not in an emergency department). Only participants admitted with a primary diagnosis of DVT were included in the analysis. If someone was noted to have DVT but was admitted to the hospital for another cause, he or she was not included in the analysis and classified as a hospital-associated DVT. A provoked DVT was defined as occurring within 90 days of a major trauma, surgery, or marked immobility or was associated with active cancer or treatment for cancer (ie, chemotherapy, radiotherapy, or surgical therapy), while an unprovoked DVT was defined as having none of the above provoking factors. A distal DVT was defined as a DVT occurring in the posterior tibial, anterior tibial, peroneal, or soleus sinuses. The primary outcome was DVT treated as an outpatient only without concurrent diagnosis of PE or VTE as a complication of hospitalization (as these individuals were not eligible for outpatient treatment at the time).
Statistical Analysis
Age, sex, race, region of residence (inside or outside the southeastern United States), education, income (determined as greater or less than $20,000 per year), and urban or rural status of residence were compared between DVT patients treated as outpatients and inpatients using χ2 analysis by inpatient or outpatient treatment. Univariable and multivariable logistic regression was then used to determine the odds ratio (OR) of receiving outpatient DVT treatment by the same variables with age per 10-year increment. ORs were adjusted for age, sex, race, year of DVT diagnosis, and region of residence as appropriate. Statistical significance was defined as P < 0.05. All statistical analyses were performed by N.A.Z. and conducted with SAS version 9.3 (SAS Institute, Cary, NC). All authors had access to the primary clinical data.
RESULTS
Over a mean of 4.7 years follow-up, 379 VTE events occurred (incident and recurrent); 185 were diagnosed with a PE, and 53 occurred as a complication of hospitalization (and were not eligible for outpatient treatment), leaving 141 DVT events potentially eligible for outpatient treatment out of a population of 29,556 participants with available records and follow-up in the cohort (Figure).
Of 141 DVT events, 39 (28%) were treated as outpatients. Table 1 presents the characteristics of participants treated as inpatients and as outpatients. Factors significantly associated with outpatient DVT treatment were younger age, female sex, white race, residing in an urban area, having a distal DVT only, and having a higher income. In the study, DVT events were recorded between 2003 and 2011; the median year of a diagnosed DVT and treated as an outpatient was 2009, while the median year of inpatient treatment was 2008. Living in the Southeast versus the rest of the country (P = 0.13) and having a high school education or greater (P = 0.07) were marginally associated with receiving outpatient treatment. In absolute terms, 11% of people living in rural areas and 19% of black patients had outpatient DVT treatment while 33% of the urban dwellers and 32% of white patients received outpatient treatment (Table 1). At the time of cohort enrollment, 92% of participants claimed to have insurance; however, this did not differentiate between Medicare, Medicaid, and private insurance. Only 1 participant diagnosed with DVT had an estimated glomerular filtration rate <30, and this individual was admitted for treatment.
Table 2 reports the multivariable adjusted OR for outpatient treatment of DVT adjusted for age, sex, race, region, and year of DVT diagnosis. Outpatient treatment of VTE was associated with younger age (OR 1.90; 95% confidence interval [CI], 1.19-3.02 for every 10 years younger in age), female sex (OR 2.41; 95% CI, 1.06-5.47), and white race (OR 3.29; 95% CI, 1.30-8.30). For each progressive calendar year in which the diagnosis was made, individuals had a 1.35-fold increase in their odds (95% CI, 1.03-1.77) of receiving outpatient treatment. Individuals living in urban areas were 4.16 (95% CI, 1.25-13.79) times more likely to receive outpatient treatment than those in rural areas. Living outside of the southeastern United States and having an income of more than $20,000 per year had increased, but nonsignificant, odds of being treated as outpatient (Table 2).
DISCUSSION
In this national, prospective, observational cohort study, only 28% of participants diagnosed with DVT were treated as outpatients versus being hospitalized. Urban area of residence, white race, female sex, and younger age were significantly associated with an increased odds of outpatient treatment. Groups that had particularly low outpatient treatment rates were rural dwellers and black participants, who had outpatient treatment rates of 11% and 19%, respectively. The odds of receiving outpatient treatment did improve over the course of the study, but in the last year of VTE assessment, outpatient treatment remained at 40%, but this was quite variable over the study years (being 8% two years prior).
