Exhibit 3.

Return-on-investment calculation.

Savings
Blood pressure reduction (among 237 patients)
Coronary heart disease (CHD)
Baseline incidence per 1000 person-years	11.4
Relative risk reduction of CHD	32.2%
Cases avoided per 1000 person-years	3.67
Cases avoided per 593 Person-years (our sample)	2.17
Total CHD cost per case	$85,181
Total CHD cost avoided	$185,020
Stroke
Baseline incidence per 1000 person-years	3.3
Relative risk reduction	44.6%
Cases avoided per 1000 person-years	1.47
Cases avoided per 593 person-years (our sample)	0.87
Total stroke cost per case	$57,618
Total stroke cost avoided	$50,234
Subtotal: savings from blood pressure reduction	$235,254
Emergency Department (ED) visits avoided
Number of patients who reported that they would have visited ED if they had not visited mobile clinic	2,851
Cost per avoidable ED visit	$474
Subtotal: ED costs avoided	$1,351,546
Total savings	$1,586,800
Expenditures
Total mobile clinic expenditures (January 2010–June 2012)	$1,222,886
Return-on-investment (Savings / Expenditures)	1.3

Source: Authors’ analysis using data reported by the National Heart, Lung, and Blood Institute, Massachusetts Department of Health Care Financing and Policy, published event-based cost estimates, and the mobile health clinic’s cost data.

Note: Methods for the step-by-step calculation of return-on-investment are described in Appendix Exhibit 2.