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#

ItemValueReference or calculation
AServer: cost of one server (3 servers needed, 1 server per 100 000 patients)USD 2000Personal communication
BServer: start-up cost (per patient)+USD 0.02Calculated from A
CServer: monthly server fees (unit cost)USD 960Personal communication
DServer: monthly fee (per patient)+USD 0.01Calculated from C
EData and phone costs per patient per monthUSD 0.21[34, 37]§
FNumber of messages per month (1 per week)4.3
GCost of a single SMS in BrazilUSD 0.02[38]
HProportion of patients who respond to SMS with a problem0.06Assumptionƒ
IProportion of patients who do not respond to first SMS0.38[11]##
JHCW time required to respond to patient who does not respond, i.e. time to send second SMS1.5 min[39]
KHCW time required to respond to patient with problem20 minAssumption¶¶
LMean, weighted HCW time per patient1.81 minCalculated as (H×K)+(I×J)
MTB nurse wage per minUSD 0.16
NSubtotal: treatment support costUSD 0.29Calculated as L×M
OMean, weighted message/phone costs associated with second SMS for patients who do not respond (to be added to all patients)USD 0.01Calculated as G×I
PMean nurse training cost (pro rata per LTBI case)USD 3.35Personal communication
TotalComplete cost for 9 months of LTBI treatment supportUSD 6.32Calculated 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.