Centers for Disease Control and Prevention

National Center for HIV, Viral Hepatitis, STD, and TB Prevention

Planning for TB Elimination using Tabby2: 

A tool to estimate state-level future TB and latent TB infection (LTBI), 

and costs associated with targeted LTBI testing and treatment

Created December 2021
Users will be able to:

▪ Estimate future state-level TB cases and LTBI prevalence

• Without additional interventions (base case scenario)

• With accelerated testing and treatment of populations at high 

risk for TB;

▪ Estimate the associated number of LTBI tests, costs, and 

benefits; and

▪ Use the estimations to set informed targets for 

progress towards TB elimination.

Objectives
Tabby 2

https://ppmltools.org/tabby2

Documentation of the Tabby2 model:

Menzies et al. 2018. “Prospects for tuberculosis elimination in the United 

States: results of a transmission dynamic model” Am J Epid. 187(9):2011-

2020. https://academic.oup.com/aje/article/187/9/2011/4995883

Estimation methods are detailed on the first page of the tool, by 

clicking "Cost Introduction" and "Further Description" from the lefthand panel. Assumptions and parameter estimates are found at: 

https://github.com/PPML/tabby2/blob/master/utilities/inst/md/Tabby2Eco

nomicAnalysisMethods.md . Users should familiarize themselves with 

the Tabby2 methods before use. 
Example: The following slides show screen 

shots from Tabby2, using Massachusetts 

(MA) as an example, to show how to use 

Tabby2 to estimate TB incidence in 2050 

under the base case scenario
▪ Under “Select a location”: Choose “Massachusetts”, then select 

“Next Page”

Select Massachusetts for Estimation
▪ Under Predefined Scenarios: Select “View Modeled Outcomes”

Estimate the Base Case
▪ Under Outcomes, select “TB Incidence per 100,000”

▪ Under Labels, select “Values”

▪ Results: 2.75/100,000 in 2020 and 1.99/100,000 in 2050 

Estimate TB Incidence in 2050 Under the Base Case Scenario
▪ Select Outcome “LTBI Prevalence (percentage)”

▪ LTBI prevalence projected at 3.74% in 2020, 2.33% in 2050

Estimate the LTBI Prevalence Percentage in 2050 

Under the Base Case Scenario
▪ Select Outcome “LTBI Prevalence (in thousands)”

▪ LTBI prevalence projected at 265,000 in 2020; 188,000 in 2050

Estimate the Number of Persons with LTBI in 2050 Under 

the Base Case Scenario
Estimate MA TB and LTBI in 2050 Under 

the “Improved LTBI Treatment (Tx)” 

Scenario
▪ Under Modeled Scenarios, select: “Improved LTBI Tx in the United 

States,” which includes for populations at high risk, a doubling of 

one-time testing, with 77.3% LTBI Tx initiation and 87.2% 

completion. This reduces the number with LTBI in MA in 2050 to 

177,000 from 188,000.

Under the “Improved LTBI Tx” Scenario, Estimate the 

Number with LTBI in 2050
▪ On the left-hand panel, Select Outcome “TB Incidence (per 100,000)” 

▪ With improved LTBI Tx, TB incidence is projected at 1.74 versus 1.99 

per 100,000 under the base case scenario in 2050

Under the “Improved LTBI Tx” Scenario, Estimate TB 

Incidence in 2050
▪ On the left-hand panel, Select Outcome “TB Incidence (in 

thousands)” 

▪ With improved LTBI Tx, TB cases are projected at 140 versus 161 

under the base case scenario in 2050

Under the “Improved LTBI Tx” Scenario, Estimate the 

Number of TB Cases in 2050
▪ Select “Time Trends” from the left-hand dark bar

▪ Re-select Outcome “TB incidence in thousands” and 

“Improved LTBI Tx” under Scenarios

Under the “Improved LTBI Tx” Scenario, Estimate TB Trends
▪ Select “Results Table” from above the graph: point estimates by year 

for the base case scenario and for the “Improved LTBI Tx” scenario 

are displayed and can be downloaded

Under the “Improved LTBI Tx” Scenario, Estimate the 

Number of TB Cases by Year
Estimate Resources Needed by MA in the 

Base Case and in the “Improved LTBI Tx” 

Scenario
▪ On the left-hand bar, select “Counts of Services” and LTBI tests (in 

thousands) and reselect the scenario “Improved LTBI Treatment”

▪ The number of LTBI tests in the base case scenario and the 

“Improved LTBI Tx” scenario are displayed

Estimate the Number of LTBI Tests in the Base Case 

and “Improved LTBI Tx” Scenarios
▪ Above the graph, select “Results Table”

▪ The number of LTBI tests in the base case and the scenario 

are displayed by year. Download the table and sum. The 30-

year total increase in LTBI tests is 87,640 with improved LTBI 

treatment vs. the base case scenario (239,670-152,030).

Estimate the Number of LTBI Tests by Year in the Base 

Case and “Improved LTBI Tx” Scenarios
▪ Under Outcomes, select “LTBI Treatment Initiations (in 

thousands).” Download the table and sum. The 30-year 

total increase in LTBI treatments is 46,960 with 

improved LTBI treatment vs. the base case scenario 

(128,450-81,490).

Estimate the Number of LTBI Treatment Starts under 

the Base Case and “Improved LTBI Tx” Scenarios
▪ On the left-hand bar, select “Input Costs”

▪ The default settings for costs are displayed. You can modify 

or keep these. IMPORTANT: then, select “Calculate Costs.” 

Give the software a few minutes to calculate.

Review or Change Input Costs 
▪ On the left-hand bar, select “Costs and Outcomes.” Reselect the “Improved LTBI 

Treatment” scenario

▪ Estimated TB cases, deaths, quality-adjusted life years (QALYs), and life years 

over 2020-2050 are in the top table. Improvements in health may yield longer 

and better lives—outcomes that can be quantified as life-years gained or QALYs 

gained.

▪ Results in the top table, second column show 476 (5,445-4,969) TB cases and in 

the third column 48 (418-370) deaths prevented. Estimated additional costs of 

the intervention ($166,502-$150,650=$15,852,000 in 2019 dollars) can be 

calculated from the “Total Health Services Cost” column in the bottom table.

Calculate Costs and Outcomes under the Base Case 

and “Improved LTBI Tx” Scenarios
▪ Cost effectiveness analysis provides information to answer: “Is the intervention the best use of 

scarce resources?” 

▪ The Incremental Cost Effectiveness Ratio (ICER)

=

Net Cost of Improved LTBI Tx − Net Cost of Base case Services

Change in TB cases with Improved LTBI Tx − Change in TB cases with Base case Services

• Where net costs equal the costs of the Improved LTBI Tx intervention or Base Case 

services minus the costs of prevented TB cases occurring under each scenario

▪ Typically, both future costs and outcomes are discounted, because money available for spending 

today is worth more than the same amount of money available for spending in the future. 

Favorable outcomes are similarly valued more today than in the future. Discounting converts all 

future costs and outcomes to their present value. Use of a social discount rate of 3% is standard. 

In Tabby2, you can select discounting under the “Cost Effectiveness” tab. Otherwise, the default 

is no discounting, which provides undiscounted costs that might be helpful for current budgeting 

purposes. 

▪ QALYs combine morbidity (for example, TB cases) and mortality (for example, deaths with TB) 

outcomes

Use Cost Effectiveness Analysis to Compare “Improved LTBI 

Tx” with the Base Case Scenario
▪ Select “View Cost Comparison” from below; Reselect the 

“Improved LTBI Tx” scenario. Select under Costing Perspective 

“Health Services costs only” and “include” discounting

▪ The ICER is displayed as $41,583 per additional TB case prevented. 

Estimate the Cost per Additional TB Case Prevented in the 

“Improved LTBI Tx” Compared with the Base Case Scenario
▪ Select a costing perspective of “health services and patient 

productivity losses.” (Note losses=costs). The ICER becomes more 

cost effective, at $4,864 per additional TB case prevented.

Change the Costing Perspective from “Health Services” to 

“Health Services and Patient Productivity Losses”
▪ Select “TB Deaths” from the left-hand menu “Effectiveness 

Measure”

▪ Displayed is the health services and patient productivity costs 

perspective, this is $49,346 per additional TB death prevented by 

the improved LTBI treatment scenario.

Estimate the Cost per Additional TB Death Prevented in the 

“Improved LTBI Tx” Compared with the Base Case Scenario
▪ Keeping the costing perspective of “health services and patient 

productivity losses” and selecting QALYs as the outcome results in 

an ICER of $37,349 per additional QALY gained.

Estimate the Cost per Additional QALY Gained in the 

“Improved LTBI Tx” Compared with the Base Case Scenario
▪ Over 30 years of doubling current LTBI one-time testing of 

persons at high risk for TB in Massachusetts:

• TB incidence could be reduced from 1.99/100K in the year 

2020 to 1.74/100K in the year 2050;

• Over the 30-year period, the number of TB cases could be 

reduced by 476; this could result in 48 fewer TB deaths;

• The estimated number of additional people tested for LTBI 

is 87,640 and treated for LTBI to reduce future TB is 46,960.

Summarize results to educate policy makers for 

improved LTBI treatment in MA to further TB elimination
Summarize results to educate policy makers for improved LTBI 

treatment in MA to further TB elimination (continued)

▪ Over 30 years of doubling current LTBI one-time testing of persons at high risk for 

TB in Massachusetts:

• The (undiscounted) healthcare system cost of this intervention is $166,502,000 

compared to $150,650,000 under current practices, an increase of $15,852,000.

• Discounting of future costs and outcomes is necessary in cost effectiveness 

analysis to account for the preference for immediate versus delayed outcomes. 

However, policy makers would want to know the estimated undiscounted 

healthcare costs of the intervention to facilitate budgeting for the intervention.
▪ Over 30 years of doubling current LTBI testing of persons at 

high risk for TB in Massachusetts, compared with that of the 

base case scenario of continuation of current level of 

prevention services, the intervention results in:

• Without including patient costs, $41,583 per 

additional TB case prevented

• Including patient costs, 

• $4,864 per additional TB case prevented

• $49,346 per additional TB death prevented

• $37,349 per additional QALY gained 

Summarize results to educate policy makers for improved 

LTBI treatment in MA to further TB elimination(continued)
▪ Tabby2 can help states estimate the future number of TB 

cases and TB deaths over 30 years, based on projections 

from historical values

▪ Tabby2 can be used with default values, or state-specific 

input costs

▪ From pre- (or user)-defined scenarios, Tabby2 computes the 

impact of increasing LTBI testing and treatment on TB cases 

prevented, TB deaths, and QALYs gained

▪ By comparing the base case with a scenario of increased LTBI 

testing/treatment, the number and cost of additional LTBI 

tests/treatments can be estimated, along with the 

preventable costs of TB cases and associated deaths

▪ This information can be compiled to make a compelling case 

for furthering TB elimination

Conclusions
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.

Funding, Acknowledgements, and Contact Information

This research was funded by the CDC, NCHHSTP Epidemiologic and Economic Modeling 

Agreement (NEEMA) (# 5U38PS004644-01)

Acknowledgements: Thank you to Jennifer Cochran, Director, Division of Global 

Populations and Infectious Disease Prevention, Bureau of Infectious Disease and 

Laboratory Sciences, Massachusetts Department of Public Health, for allowing use of 

state data as an example in this presentation, and to Nicole Swartwood at the 

Harvard TH Chan Prevention Policy Modeling Lab for creating the tool.

Contact Nicole Swartwood at nswartwood@hsph.harvard.edu or Suzanne Marks at 

smarks@cdc.gov for further information.