Background
Methods
Screening strategies
Strategy | Pre-travel tuberculin skin test results | Interpretation of pre-travel results | Intervention | |
---|---|---|---|---|
Test 1 | Test 2 | |||
Pre-trip two step tuberculin test Treat converters | ≥ 10 mm | N/A | Baseline latent tuberculosis infection (LTBI) | No intervention. Passive diagnosis of TB disease pursued if symptomatic post-travel. |
<10 mm | ≥ 10 mm | Booster effect; no baseline LTBI | No intervention. Passive diagnosis of TB disease pursued if symptomatic post-travel. | |
<10 mm | <10 mm | No LTBI | Post-trip tuberculin test. Converters prescribed isoniazid. | |
Pre-trip two step tuberculin test Treat reactors and converters | ≥ 10 mm | N/A | Baseline LTBI | Prescribe isoniazid. |
<10 mm | ≥ 10 mm | Booster effect | No intervention. Passive diagnosis of TB disease pursued if symptomatic post-travel | |
<10 mm | <10 mm | No LTBI | Post-trip tuberculin test. Converters prescribed isoniazid | |
Post-trip tuberculin test | None | None | One post-trip tuberculin skin test. All reactors (≥ 10 mm) prescribed isoniazid. | |
Post-trip chest x-ray | None | None | Chest x-ray post-trip. Persons with radiographic abnormalities compatible with TB, negative workup for active TB, and TST ≥ 5 mm prescribed isoniazid. | |
No screening | No intervention before or after trip. Passive diagnosis of TB disease pursued if symptomatic post-travel. |
The decision analysis model
Base value | Range | Sources | |
---|---|---|---|
Annual risk of progression from latent tuberculosis (LTBI) to TB disease | |||
Among persons newly infected during travel | |||
First two years after infection | 0.025 | 0.02 – 0.05 | [33] |
Subsequently | 0.001 | 0.001 – 0.002 | [34] |
Among persons with LTBI before travel, given | |||
No underlying radiographic abnormalities [see below] | 0.001 | [34] | |
Underlying radiographic abnormalities [see below] | 0.0066 | [34] | |
Reduction in risk afforded by: | |||
Full 9 months of isoniazid, given drug-sensitive latent infection | 90% | [35] | |
<6 months isoniazid | 0% | [36] | |
Previous LTBI, among persons who are reinfected during travel | 79% | [37] | |
Prevalence of isoniazid resistance | |||
Mexico | 0.072 | 0.072 – 0.12 | [38, 39] |
Dominican Republic | 0.198 | -- | [40] |
Haiti | 0.159 | -- | [41] |
Active TB | |||
Proportion of travelers with active TB symptomatic upon return | 0.27 | 0.11 – 0.44 | [21, 26] |
Probability of hospitalization given active TB diagnosed after symptoms | 0.8 | [42] | |
Probability of hospitalization given active TB diagnosed through screening | 0.5 | [21, 22] | |
Probability of completing full anti-TB therapy | 1.0 | assumed | |
Risk of major side effect with full anti-TB therapy | 0.051 | 0.01 – 0.1 | [43] |
Probability of death, given major treatment side effect | 0.015 | 0.001 – 0.032 | [43–45] |
Treatment of latent TB infection | |||
Probability of completing 9 months isoniazid | 0.647 | 0.62 – 1 | [10, 46] |
Probability of major side effect with isoniazid | 0.003 | [43–45] | |
Probability of death, given major treatment side effect | 0.015 | 0.001 – 0.032 | [43–45] |
Tuberculin skin testing | |||
Probability of boosting, given previous BCG vaccination | 0.25 | [17] | |
Specificity for LTBI | 0.875 | - | [17] |
Sensitivity for LTBI | 0.99 | - | [47, 48] |
Sensitivity for active TB | 0.88 | - | [48] |
Probability of loss to follow-up between pre- and post- travel evaluations, for repeat testing strategies | 0.34 | [7] | |
Probability of abnormal chest X-ray upon return from travel | |||
With preexisting LTBI | 0.11 | 0.07 – 0.15 | [33, 34, 49, 50] |
With LTBI newly acquired during travel | 0 | assumed | |
With active TB | 0.95 | 0.9 – 1 | [51, 52] |
Sputum cultures (3) for M. Tuberculosis
| |||
Specificity | 0.99 | [51] | |
Sensitivity | 0.9 | [53] | |
Costs for TB screening and care in the US (expressed in 2005 US dollars) | |||
Initial clinic visit | $68 | [54, 25] | |
Tuberculin skin test | $12 | [42, 23] | |
Follow-up clinic visit after tuberculin test | $36 | [42] | |
Chest radiograph with reading | $36 | [42] | |
Isoniazid, 9 months supply | $25 | [54] | |
7 outpatient clinic visits during isoniazid treatment | $385 | [54] | |
Major adverse reaction to isoniazid | $9,834 | [54] | |
3 sputa for AFB smear and culture, after abnormal CXR | $126 | [55, 56] | |
Inpatient treatment of active TB disease | $9,061 | [57] | |
Outpatient treatment of active TB disease | $2,600 | [42] | |
Contact investigation and management, per active TB case (identified via screening) | $4,483 | [42, 24] |
Travelers
BCG vaccination
Secondary transmission
Loss to follow-up
Costs
Sensitivity analyses
Research ethics
Results
Base case analysis
Traveler's destination Traveler group: Annual risk of infection Screening strategy from least to most expensive | Expected costs per 1,000 (2005 USD) | Expected cases per 1,000 | Incremental cost per 1,000†
| Incremental cases prevented per 1,000†
| Incremental cost per case prevented†
|
---|---|---|---|---|---|
Travelers to Mexico
| |||||
US-born: Annual infection risk 0.3% | |||||
No screening | $7,428 | 1.0 | - | - | - |
Post-trip TST | $47,082 | 0.8 | $39,654 | 0.2 | $161,196 |
Post-trip chest x-ray | $58,972 | 0.9 | $11,890 | (0.1) | Dominated |
Pre & post trip TST; treatment for reactors | $68,644 | 0.8 | $9,672 | 0.1 | Dominated |
Pre & post trip TST; treatment for converters only | $68,741 | 0.9 | $97 | (0.1) | Dominated |
Mexican-born: Annual infection risk 0.3% | |||||
No screening | $9,855 | 1.3 | - | - | - |
Post-trip TST | $57,666 | 1.0 | $47,811 | 0.3 | $143,578 |
Post-trip chest x-ray | $61,087 | 1.1 | $3,421 | (0.1) | Dominated |
Pre & post trip TST; treatment for converters only | $71,335 | 1.2 | $10,248 | (0.1) | Dominated |
Pre & post trip TST; treatment for reactors | $74,372 | 1.1 | $3,037 | 0.1 | Dominated |
Travelers to Dominican Republic
| |||||
US-born: Annual infection risk 0.8% | |||||
No screening | $13,226 | 1.7 | - | - | - |
Post-trip TST | $51,961 | 1.3 | $38,735 | 0.4 | $102,745 |
Post-trip chest x-ray | $64,678 | 1.6 | $12,718 | (0.3) | Dominated |
Pre & post trip TST; treatment for reactors | $73,792 | 1.4 | $9,114 | 0.2 | Dominated |
Pre & post trip TST; treatment for converters only | $73,889 | 1.5 | $97 | (0.1) | Dominated |
Dominican-born: Annual infection risk 0.8% | |||||
No screening | $25,423 | 3.3 | - | - | - |
Post-trip TST | $73,523 | 2.6 | $48,100 | 0.7 | $65,264 |
Post-trip chest x-ray | $75,711 | 2.9 | $2,188 | (0.3) | Dominated |
Pre & post trip TST; treatment for reactors | $86,604 | 2.8 | $10,893 | 0.1 | Dominated |
Pre & post trip TST; treatment for converters only | $89,568 | 3.2 | $2,964 | (0.4) | Dominated |
Travelers to Haiti
| |||||
US-born: Annual infection risk 2.6% | |||||
No screening | $34,041 | 4.4 | - | - | - |
Post-trip TST | $68,756 | 3.5 | $34,715 | 0.9 | $36,931 |
Post-trip chest x-ray | $85,163 | 4.3 | $16,407 | (0.8) | Dominated |
Pre & post trip TST; treatment for reactors | $91,797 | 3.8 | $6,634 | 0.5 | Dominated |
Pre & post trip TST; treatment for converters only | $91,893 | 3.9 | $96 | (0.1) | Dominated |
Haitian-born: Annual infection risk 2.6% | |||||
No screening | $73,594 | 9.6 | - | - | - |
Post-trip chest x-ray | $119,983 | 8.5 | $46,389 | 1.1 | $40,585* |
Post-trip TST | $121,073 | 7.4 | $1,090 | 1.1 | $1,014 |
Pre & post trip TST; treatment for reactors | $133,556 | 8.1 | $12,484 | (0.7) | Dominated |
Pre & post trip TST; treatment for converters only | $135,395 | 9.2 | $1,839 | (1.1) | Dominated |
Sensitivity Analyses
All costs in 2005 US dollars | |||||||
---|---|---|---|---|---|---|---|
Mexico | Dominican Republic | Haiti | |||||
Annual risk of infection 0.3% | Annual risk of infection 0.8% | Annual risk of infection 2.6% | |||||
US-born | Mexican-born | US-born | Dominican-born | US-born | Haitian-born | ||
Base case | $161,196 | $143,578 | $102,745 | $65,264 | $36,931 | $21,406 | |
Increase traveler age from 21 years† | to 35 years | $163,779 | $148,268 | $103,993 | $67,644 | $37,482 | $22,651 |
to 55 years | $178,237 | $164,591 | $113,168 | $76,263 | $40,989 | $26,537 | |
Increase trip duration from 3 months† | to 6 months | $111,832 | $60,889 | $16,787 | $108,476 | $48,731 | $15,261 |
to 12 months | $67,592 | $71,720 | $31,427 | $31,217 | $5,426 | $8,554 | |
to 24 months | $35,872 | $41,050 | $13,622 | $16,510 | Cost saving | $2,740 | |
Change isoniazid completion rate from 65%† | to 50% | $208,386 | $185,056 | $132,752 | $84,964 | $48,813 | $29,113 |
to 100% | $103,191 | $93,192 | $65,368 | $41,179 | $22,017 | $12,007 |