TB Isolation Cost Estimation

Estimates hospitalization, tracing, and productivity costs for TB isolation scenarios, comparing 14-day vs. 5-day isolation protocols.

Authors: Edward Wang, Olivia Banks

Model id: tb_isolation. Open it in the app with ?model=tb_isolation; see Sharing links.

About this model

Overview

This calculator compares the economic impact of two tuberculosis isolation protocols: 14-day isolation (standard) versus 5-day isolation (shortened). The model accounts for direct isolation costs, lost productivity, and the long-term costs of secondary TB infections.

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Scenarios

• 14-day Isolation: Standard isolation protocol for infectious TB patients
• 5-day Isolation: Shortened isolation protocol (increases secondary transmission risk)

Key Model Components

1. Secondary Infection Estimation: Models latent and active TB cases resulting from reduced isolation time
2. Direct Costs: Daily costs vary by isolation setting (hospital, motel, or home)
3. Productivity Loss: Lost wages during isolation period (index case only)
4. Secondary Infection Costs: Long-term costs of treating latent and active TB in contacts, with appropriate discounting over remaining years of life

Transmission Risk Impact

Reducing isolation duration increases the infectious period, leading to more secondary cases:

Economic Impact Summary

The trade-off between isolation duration and transmission risk creates complex economic dynamics:

• Short-term savings: Reduced isolation costs and productivity losses
• Long-term costs: Higher burden from secondary infections
• Net effect: Often favors longer isolation from a societal cost perspective

Assumptions

• All costs are in USD
• Shortened isolation increases infectiousness by a multiplier
• Latent TB progression to active disease occurs in two phases: first 2 years and remainder of lifetime
• Future costs are discounted at the specified discount rate
• Productivity loss assumes 8-hour workdays

Parameters

Transmission

Parameter	Default	Unit	Range or choices	Sources
Number of contacts for each released TB case contacts_per_case Average number of close contacts exposed to each TB patient upon release from isolation.	141.5	contacts	0 to 500	CDC TB contact investigation guidelines.
Probability that contact develops latent TB if 14-day isolation prob_latent_if_14_day Baseline probability that an exposed contact develops latent TB infection when the index case completes 14-day isolation.	0.02	proportion	0 to 1	TB transmission studies (standard isolation protocol).
Multiplier for infectiousness with 5-day vs. 14-day isolation infectiousness_multiplier Factor by which infectiousness increases when using 5-day instead of 14-day isolation.	1.5	multiplier	0 to 10	Modeling studies of TB isolation duration and transmission risk.

Disease Progression

Parameter	Default	Unit	Range or choices	Sources
First 2 years prob_latent_to_active_2yr Probability that latent TB progresses to active disease within the first 2 years after infection.	0.05	proportion	0 to 1	Horsburgh CR Jr. (2004). Priorities for the treatment of latent tuberculosis infection. NEJM.
Rest of lifetime (prob_latent_to_active_lifetime) prob_latent_to_active_lifetime Probability that latent TB progresses to active disease during the remainder of the person's life (after first 2 years).	0.05	proportion	0 to 1	Horsburgh CR Jr. (2004). Priorities for the treatment of latent tuberculosis infection. NEJM.

Isolation Costs

Parameter	Default	Unit	Range or choices	Sources
Isolation type isolation_type Type of isolation setting for the patient.	HOME_ISO		HOSP_ISO = Hospital MOTEL_ISO = Motel, with nurse HOME_ISO = Home, with nurse

Isolation Costs - Hospital

Parameter	Default	Unit	Range or choices	Sources
Direct medical cost of a day of isolation direct_medical_cost_day Daily direct medical cost for hospital isolation (used when isolation_type=HOSP_ISO and >0).	3,996	USD/day	0 to 20,000	Hospital cost data for TB isolation rooms.
Daily isolation cost isolation_cost Daily cost for hospital isolation (used when isolation_type=HOSP_ISO and direct_medical_cost_day=0).	85	USD/day	0 to 10,000

Isolation Costs - Motel / Home

Parameter	Default	Unit	Range or choices	Sources
Cost of motel room per day motel_room_cost Daily cost of motel room rental for isolation (used when isolation_type=MOTEL_ISO).	150	USD/day	0 to 1,000
Hourly wage for nurse hourly_wage_nurse Hourly wage for nurse conducting check-ins for motel or home isolation.	42.42	USD/hour	0 to 200	Bureau of Labor Statistics median for registered nurses (2024).
Time for nurse to check in w/ pt in motel or home (hrs) nurse_checkin_hours Hours required for each nurse check-in visit (including travel time).	2	hours	0 to 24

Secondary Infection Costs

Parameter	Default	Unit	Range or choices	Sources
Cost of latent TB infection cost_latent Direct medical cost of diagnosing and treating one case of latent TB infection.	300	USD	0 to 10,000	CDC TB treatment cost estimates.
Cost of active TB infection cost_active Direct medical cost of treating one case of active TB disease, including hospitalization, medications, and monitoring.	34,523	USD	0 to 100,000	Marks SM et al. (2014). Costs of active tuberculosis treatment in the United States. IJTLD.
Discount rate discount_rate Annual discount rate for calculating present value of future costs (typically 3% for health economics).	0.03	proportion	0 to 0.1	Standard health economics discount rate (3% per year).
Remaining years of life remaining_years_of_life Expected remaining years of life for TB patients/contacts (used to calculate discounted lifetime costs).	40	years	1 to 100

Productivity

Parameter	Default	Unit	Range or choices	Sources
Hourly wage for worker hourly_wage_worker Average hourly wage for calculating lost productivity during isolation.	29.36	USD/hour	0 to 500	U.S. Bureau of Labor Statistics (2024).
Ratio of workdays to total days workday_ratio Fraction of days that are workdays (accounting for weekends and holidays).	0.714	proportion	0 to 1

Set per scenario

Each scenario supplies its own value for these; the default applies to scenarios added in the app.

Parameter	Default	Unit	Range or choices	Sources
Days of isolation isolation_days Number of days the patient is isolated.	14	days	1 to 60
Latent infection multiplier latent_multiplier Multiplier for the probability of latent TB infection relative to the 14-day baseline.	1	multiplier	0 to 10

Scenarios

Scenario	Days of isolation	Latent infection multiplier
14-day Isolation 14_day	14	1
5-day Isolation 5_day	5	1.5

Presets

Preset	Changes
Congregate setting (prison/shelter) congregate_setting	contacts_per_case = 300 prob_latent_if_14_day = 0.05 hourly_wage_worker = 18
Community setting community_setting	contacts_per_case = 75 prob_latent_if_14_day = 0.015
Low-resource setting low_resource	contacts_per_case = 200 prob_latent_if_14_day = 0.04 direct_medical_cost_day = 120 cost_latent = 80 cost_active = 4,200 hourly_wage_worker = 4.5 hourly_wage_nurse = 8

Equations

Evaluated in order; each can use the parameters and any equation above it.

Baseline latent TB infections (cases) eq_latent_baseline

contacts_per_case * prob_latent_if_14_day

Latent TB infections (cases) eq_latent

eq_latent_baseline * latent_multiplier

Active TB disease (cases) eq_active

eq_latent * prob_latent_to_active_2yr + eq_latent * (1 - prob_latent_to_active_2yr) * prob_latent_to_active_lifetime

Daily isolation cost (USD/day) eq_daily_cost

(direct_medical_cost_day if (isolation_type == "HOSP_ISO" and direct_medical_cost_day > 0) else (isolation_cost if isolation_type == "HOSP_ISO" else (motel_room_cost + hourly_wage_nurse * nurse_checkin_hours if isolation_type == "MOTEL_ISO" else hourly_wage_nurse * nurse_checkin_hours)))

Direct cost of isolation (USD) eq_direct

eq_daily_cost * isolation_days

Lost productivity (USD) eq_productivity

isolation_days * workday_ratio * hourly_wage_worker * 8

Discounted 2-year progression probability (dimensionless) eq_discounted_2yr

(prob_latent_to_active_2yr / 2) / ((1 + discount_rate) ** 1) + (prob_latent_to_active_2yr / 2) / ((1 + discount_rate) ** 2)

Cost per latent case (with discounting) (USD) eq_secondary_cost_per_latent

cost_latent + cost_active * (eq_discounted_2yr + sum((prob_latent_to_active_lifetime / remaining_years_of_life) / ((1 + discount_rate) ** y) for y in range(3, remaining_years_of_life + 1)))

Cost of secondary infections (USD) eq_secondary

eq_latent * eq_secondary_cost_per_latent

Total cost (USD) eq_total

eq_direct + eq_productivity + eq_secondary