TABLE 2

Digital technology costs for treatment support using two-way short message service (SMS), per person with latent tuberculosis infection (LTBI), in 2016 USD#

 Item Value Reference or calculation A Server: cost of one server (3 servers needed, 1 server per 100 000 patients) USD 2000 Personal communication¶ B Server: start-up cost (per patient)+ USD 0.02 Calculated from A C Server: monthly server fees (unit cost) USD 960 Personal communication¶ D Server: monthly fee (per patient)+ USD 0.01 Calculated from C E Data and phone costs per patient per month USD 0.21 [34, 37]§ F Number of messages per month (1 per week) 4.3 G Cost of a single SMS in Brazil USD 0.02 [38] H Proportion of patients who respond to SMS with a problem 0.06 Assumptionƒ I Proportion of patients who do not respond to first SMS 0.38 [11]## J HCW time required to respond to patient who does not respond, i.e. time to send second SMS 1.5 min [39] K HCW time required to respond to patient with problem 20 min Assumption¶¶ L Mean, weighted HCW time per patient 1.81 min Calculated as (H×K)+(I×J) M TB nurse wage per min USD 0.16 N Subtotal: treatment support cost USD 0.29 Calculated as L×M O Mean, weighted message/phone costs associated with second SMS for patients who do not respond (to be added to all patients) USD 0.01 Calculated as G×I P Mean nurse training cost (pro rata per LTBI case) USD 3.35 Personal communication¶ Total Complete cost for 9 months of LTBI treatment support USD 6.32 Calculated as B+(9×(D+E+(F×G)))+N+O+P per person

HCW: healthcare worker; TB: tuberculosis. #: the aggregate cost does not include cost components related to diagnosis or treatment (see table 3). : Richard Lester (University of British Columbia, Vancouver, BC, Canada) from the WelTel trial [34]. +: Brazil has ∼70 000 new active TB cases per year; assuming four contacts per case, we assumed that 280 000 contacts per year would receive treatment in 4745 TB clinics [40]. §: calculated as clinic cost/mean number of patients per clinic (WelTel)/36 months (length of WelTel trial). ƒ: equivalent to total adverse event rates for LTBI. ##: assumed from the reported global LTBI treatment completion rate, conditional on initiating treatment. ¶¶: time on the phone is assumed to be equivalent to in-person adverse event consultation.