Tuberculosis Risk in the Returning Traveler: Assessing Tuberculosis Test Conversion Among Routinely Tested Patients at an Asian American Health Center

Abstract

Background

In the United States, testing for latent tuberculosis (TB) infection is recommended for persons from higher-TB-prevalence countries, but guidelines do not address repeat testing for persons with international travel.

Methods

Using 2010–2022 data from a Californian federally qualified health center serving an Asian American population, we measured the incidence of TB test conversion (negative to positive result) and proportion of test converters receiving treatment among routinely tested patients (ie, patients with no history of TB infection, at least one prior negative result, and annual or biennial TB testing). We performed a nested case–control study to measure the association between TB test conversion and travel outside the United States.

Results

Of 5668 patients receiving routine TB testing at annual/biennial frequencies, conversions occurred in 117 patients with TB skin tests (2.9%) and 52 patients with interferon-gamma release assays (3.2%); the overall test conversion incidence rate was 2.1/100 person-years. Latent TB infection treatment was initiated in 57% of test converters. Two patients were diagnosed with TB disease after test conversion, representing a 2-year TB incidence rate of 0.35/100 person-years. Patients with documented international travel had a 1.95-fold increased odds of TB test conversion (95% confidence interval 1.07–3.57) compared to patients without documented travel, with most travel occurring in medium or high-TB-prevalence countries.

Conclusions

Within a 13-year study period, among a routinely tested population at higher risk of TB infection due to race and nativity, risk of TB test conversion was low. However, recent travel to higher-TB-prevalence settings nearly doubled the odds of TB test conversion.

This nested case–control study examined the association between recent international travel and TB test conversion among a routinely tested, predominantly Asian American clinic population in California. TB test conversion was nearly twice as likely among those with recent travel to higher TB prevalence countries in comparison to those without

Graphical Abstract

Graphical Abstract.

The incidence of tuberculosis (TB) disease represents a health disparity in the United States. Risk is concentrated in persons born outside the United States, and 39% of non-US-born cases occur in people who identify as Asian [1]. Although the US Preventive Services Task Force (USPSTF) recommends testing for TB infection in adults who were born or resided in countries with a high-TB prevalence, uptake in primary care has been low; in a nationwide estimate, less than a quarter of patients with risk factors received appropriate testing [2]. Additionally, guidelines largely do not address the question of serial testing for TB infection among those who travel to countries with high-TB prevalence [3]. There are data suggesting that among immigrants to low-TB-prevalence countries, recent travel to home countries is associated with increased risk of developing TB disease; thus, serial TB testing could potentially impact both patient care and public health [4, 5].

North East Medical Services (NEMS) is a federally qualified health center in the San Francisco Bay Area serving over 80 000 people annually, many of whom are non-US-born, identify as Asian, and travel frequently to countries such as China, Vietnam, and the Philippines. North East Medical Services offers comprehensive primary care services with language-concordant providers. Since 2010, recognizing TB as a major health disparity affecting its patient population, NEMS led a series of clinic-directed interventions for TB prevention [6]. With a patient population at higher risk for TB disease due to nativity, we performed a retrospective analysis aiming to describe TB test conversion and associated risk factors, including travel.

METHODS

Patient Population, Selection, and Measurements

In partnership between California Department of Public Health (CDPH) and NEMS, we retrospectively assessed clinical data from 1 January 2010 and 30 September 2022 to describe the demographics of patients with TB test conversion (hereafter known as “test converters” or “converters”) and to measure the incidence of TB test conversion, the association between TB test conversion and travel, the proportion of test converters who received latent TB infection (LTBI) evaluation and treatment, and incidence of TB disease among test converters.

We extracted information on test date, test type, interpretive test result, quantitative interferon-gamma release assay (IGRA) result, sex, date of birth, ethnicity, race, birthplace, preferred language, year and month of entry to the United States, pregnancy, history of single-room occupancy (SRO) residence, travel outside of the United States, history of exposure to a person with TB disease, immunosuppression, employment in healthcare, chest imaging information, medications, and treatment completion from the electronic health records (EHR). We identified pregnancy status by comparing test date against a 280-day window, back-calculated from the expected delivery date and modified by known delivery date, if available [7].

Patients were eligible for inclusion in the analysis if they had at least 2 tests of the same type (IGRA or TB skin test [TST]), no history of TB or LTBI diagnosis or treatment, and an initial negative test result. We considered tests eligible for analysis if they were 30 or more days apart and there were no tests with unknown or indeterminate results occurring between them. For patients with 2 or more IGRA results, we preferentially analyzed IGRA results due to their higher specificity for TB infection in non-US-born persons; we disregarded any preceding TST, regardless of result. In order to investigate the impact of travel on TB test conversion, we sought to identify a population that was serially tested due to employment, school, or tenancy requirements, rather than risk-based testing. We created a retrospective cohort of “routine testers,” defined as having 3 or more TB tests of the same type at approximately annual or biennial frequency; these patients were selected because their testing cadence suggested mandated serial testing for work or school, rather than risk-based testing. Test conversion occurred when an initially negative test (or multiple negative tests) changed to a positive test of the same test type, within the study period. For TST converters, we used EHR documentation of “positive TST,” or a 10 mm or greater change. For IGRA converters, we used the interpretive “positive” result from EHR. When available, we recorded quantitative results. All IGRA testing performed in NEMS clinics used the QuantiFERON (QFT) assay. We defined “low-positive” IGRA results as a TB antigen minus nil (TB Ag-Nil) range of 0.35–0.70 IU/mL and “high-positive” IGRA results as TB Ag-Nil ≥0.71 IU/mL [8–11].

We performed a nested case–control study within our cohort of routine testers and conducted a chart review to improve data completeness on reasons for testing, pregnancy, international travel, history of close contact to a person with TB disease, symptoms, TB disease or LTBI diagnoses, referrals, and treatment. Each patient with TB test conversion was randomly matched to up to 3 patients who did not convert, hereafter, “non-converters,” based on sex, age ±5 years, test date ±6 months from the second test date, and history of SRO residence. Single-room occupancy residence, in contrast to homelessness, is not listed as a TB risk factor by the San Francisco Department of Public Health and was not considered a reason for exclusion. Non-converters could be sampled more than once. When a non-converter became ineligible during chart review and back-up non-converters were available, additional non-converters were randomly sampled for replacement.

Finally, we matched all eligible study patients with a TB test conversion to the California TB Disease Registry records from 2010 to 2023 using date of birth, sex, first name, last name, and zip code to determine whether TB disease occurred after test conversion. Tuberculosis disease incidence rates were calculated for 2 distinct populations postinfection: (1) test converters within the routine tester cohort and (2) test converters among all eligible patients with at least 2 tests of the same type, as a comparator. We approximated the infection date as the midpoint between the first negative test and the subsequent positive test of the same type. Test converters with tests <60 days apart were excluded from analysis, as these patients were generally persons who had developed symptoms of TB disease and received their second test in the context of TB disease diagnosis.

Here onward, we may refer to these 3 key analyses and their respective populations as Group A (routine tester cohort), Group B (chart-reviewed nested case–control study group), and Group C (all test converters, among any patients with 2 tests of the same type).

Analysis

In group A, the routine tester cohort, we performed analyses to determine (1) the distribution of test converters across age, sex, race, ethnicity, birthplace, SRO history, and history of employment in healthcare; (2) the incidence of TST conversion; (3) the incidence of IGRA conversion; (4) the proportion of IGRA converters with low-positive quantitative results who subsequently reverted; and (5) the proportion of test converters who received LTBI treatment. In groups A and C, we estimated the incidence rates of TB disease progression among test converters at 1, 2, and 5 years postinfection.

In group B, the nested case–control study group, we used conditional logistic regression to estimate the association between travel and test conversion. Potential confounding by age, sex, SRO residence, and secular or long-term population trends were accounted for in the matching. We conducted sensitivity analysis on the estimated odds ratio of test conversion to gauge the influence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic and replacement of non-converter patients who became ineligible for the study during chart review.

Patient Consent Statement

This study was reviewed and approved by the Institutional Review Board (IRB) of the Association of Asian Pacific Community Health Organizations and the Committee from Protection of Human Subjects (CPHS) at the State of California Health and Human Services Agency. The study protocol was reviewed and in compliance with ethical guidelines for research involving human subjects; both the IRB and CPHS stated the analysis posed minimal risks. A Data Use Agreement was signed by CDPH and NEMS, ensuring all parties were in compliance with applicable administrative, physical, and electronic safeguards outlined by CPHS to protect personal health information.

RESULTS

Within the study population of 62 018 patients, 14 730 patients were eligible with at least 2 tests of the same type (Figure 1). In this eligible cohort, 632 patients converted from negative to positive test results (group C) and were matched to the TB disease registry to examine disease incidence. Among the eligible cohort, we identified 5668 patients who met our study definition for routine testing (group A). A total of 169 (3.0%) of the routine testers converted from negative to positive within the study period. After the matching process, 135 test converters and 405 test non-converters were selected for chart review and the nested case–control study. Due to resampling of non-converters during the matching, 497 unique patients were represented in this population. After chart review, 83 patients were excluded due to newly identified ineligibility (ie, documented risk of TB exposure) or being matched to a newly ineligible converter. We chart-reviewed 7 additional patients as backups to newly ineligible non-converters. For the 504 total patients who underwent chart review, medical records indicated that 83% (417/504) were routinely tested in the context of physical examinations, employment, or school-based requirements, 10% (51/504) were tested due to pregnancy, 3% (14/504) due to travel, 2% (8/504) due to contact with an infectious TB patient, 1% (6/504) due to TB disease symptoms, and 1% (7/504) for unknown reasons (Supplementary Table 1). We excluded patients whose chart review indicated that they were tested for potentially risk-based reasons (TB symptoms, contact, and travel), resulting in a final nested case–control study sample size of 457 represented by 430 unique patients (Group B).

Figure 1.

A, Flow diagram of routine tester cohort and all test converter cohort. B, Flow diagram of chart-reviewed nested case–control study group.

Of the 5668 group A routine testers, 63% were children (<18 years old) at the time of their second TB test, 94% were Asian, 41% were US-born, and 5% had a history of SRO residence (Table 1). Interferon-gamma release assay conversions occurred in 3.2% (52/1621) of routine testers, while TST conversions occurred in 2.9% (117/4047). The majority of patients routinely tested with TST were children (79%, 3216/4047); the majority of patients tested with IGRA were adults (78%, 1265/1621). In children, the proportion of TST test conversion was highest among those aged 5–17 years (7.9%, 34/428). Among adults, TST conversions increased in each age bracket up to 35–44 years (8.3%, 11/133) and then declined. The proportion of adults with IGRA conversions increased in each age bracket up to 65–84 years (5.4%, 6/112). IGRA conversions in children were infrequent. Among patients with documented place of birth, TB test conversions occurred in a greater proportion of non-US-born patients (4.4%, 129/2941) than US-born patients (1.2%, 27/2321); this difference was more pronounced for TST conversions (5.3% non-US-born vs 1.2% US-born) than for IGRA conversions (3.4% non-US-born vs 1.3% US-born). Tuberculosis test conversions among those with documentation of SRO residence, pregnancy, or history of employment in healthcare occurred in 15 or less patients each. The incidence rate of TB test conversion was 2.1 per 100 person-years (py) overall, 1.8 per 100 py for IGRA, and 2.2 per 100 py for TST.

Table 1.

Proportion of Test Conversion Among Group A Routine Testers by Demographics and Risk Factors

	Overall			TB Skin Test			IGRA
	Total	n	Proportion Converted (%)	Total	n	Proportion Converted (%)	Total	n	Proportion Converted (%)
Overall	5668	169	3.0	4047	117	2.9	1621	52	3.2
Age (y)
≤4	2883	44	1.5	2788	44	1.6	95	0	0
5–17	689	37	5.4	428	34	7.9	261	3	1.1
18–24	371	9	2.4	190	5	2.6	181	4	2.2
25–34	712	27	3.8	303	15	5.0	409	12	2.9
35–44	373	22	5.9	133	11	8.3	240	11	4.6
45–64	493	22	4.5	172	6	3.5	321	16	5.0
65–84	144	8	5.6	32	2	6.2	112	6	5.4
≥85	3	0	0	1	0	0	2	0	0
Sex
Female	3415	103	3.0	2221	64	2.9	1194	39	3.3
Male	2253	66	2.9	1826	53	2.9	427	13	3.0
Race
Asian	5336	160	3.0	3804	111	2.9	1532	49	3.2
Black	35	0	0	27	0	0	8	0	0
Multi-race	22	1	4.5	16	0	0	6	1	16.7
Native American	5	0	0	3	0	0	2	0	0
Pacific Islander	16	1	6.2	9	1	11.1	7	0	0
White	124	1	0.8	87	0	0	37	1	2.7
Unknown	130	6	4.6	101	5	5.0	29	1	3.4
Ethnicity
Hispanic	63	0	0	45	0	0	18	0	0
Non-Hispanic	3851	119	3.1	2665	81	3.0	1186	38	3.2
Unknown	1754	50	2.9	1337	36	2.7	417	14	3.4
Birthplace
Born in US	2321	27	1.2	2170	25	1.2	151	2	1.3
Born outside of US	2941	129	4.4	1531	81	5.3	1410	48	3.4
Unknown	406	13	3.2	346	11	3.2	60	2	3.3
History of SRO residence
No	5412	159	2.9	3907	113	2.9	1505	46	3.1
Yes	256	10	3.9	140	4	2.9	116	6	5.2
Pregnancy at time of second test
No	1092	43	3.9	547	27	4.9	545	16	2.9
Yes	287	15	5.2	21	5	23.8	266	10	3.8
Not applicable	4289	111	2.6	3479	85	2.4	810	26	3.2
History of employment in healthcare
No	5643	167	3.0	4039	115	2.8	1604	52	3.2
Yes	25	2	8.0	8	2	25.0	17	0	0

Total indicates the total number of group A routine testers in the category, n indicates the number of routine testers who converted from negative to positive results in the category, and the proportion converted column indicates the proportion of routine testers in the category who converted test results. The “not applicable” category in the pregnancy section includes all patients who are not reproductive-aged (15–49 y old) females. See Figure 1A for derivation of the group A routine tester cohort included in these results. Italics indicate percentages.

Abbreviations: IGRA, interferon-gamma release assay; SRO, single-room occupancy; TB, tuberculosis; TST, tuberculin skin test.

Among IGRA conversions within routine tester Group A, stratified by quantitative values, 21% (11/52) were low-positive, 17% (9/52) were high-positive, and 62% (33/52) had unknown values (Table 2). A total of 17% (9/52) of IGRA converters later reverted to negative; of these, 44% (4/9) had initial low-positive IGRA values, 11% (1/9) had high positives, and 44% (4/9) had positive IGRA results with unknown quantitative values. Among routine test converters, incident TB disease was reported in 2 patients, for a 2-year incidence rate of 0.35 per 100 py and a 5-year incidence rate of 0.31 per 100 py (Table 3). Among all 632 group C converters, incident TB disease was reported in 8 patients, yielding a 2-year incidence rate of 0.57 per 100 py and a 5-year incidence rate of 0.30 per 100 py. Among patients with incident TB disease, 6 were tested with IGRA; 4 had quantitative values available for review, all of which were high positive.

Table 2.

Routine IGRA Test Conversions and Reversions Stratified by Quantitative IGRA Values

	n	%
Routine IGRA test converters
Total	52	100
Low-positive (0.35–0.70 IU/mL)	11	21
High-positive (0.71–max IU/mL)	9	17
Positive with unknown TB Ag minus nil	32	62
Routine IGRA test reverters
Total	9	100
Low-positive (0.35–0.70 IU/mL)	4	44a
High-positive (0.71–max IU/mL)	1	11a
Positive with unknown TB Ag minus nil	4	44a

Abbreviations: IGRA, interferon-gamma release assay; TB, tuberculosis.

^aEstimates are based on sparse data and are unstable.

Table 3.

TB Disease Incidence Rates Among Group A and C Test Converters

	Group A. Routine Test Converters			Group C. All Test Converters
Years since infectiona	Person-time (y)	N	Incidence of TB disease (per 100 py)	Person-time (y)	N	Incidence of TB disease (per 100 py)
1	143	0	0	618	5	0.809b
2	285	1	0.351c	1231	7	0.569b
5	640	2	0.313c	2719	8	0.294b

Excludes test converters with tests <60 d apart.

Abbreviations: py, person-years; TB, tuberculosis.

^aDate of infection was assumed to occur at the midpoint between the date of the negative first test and the positive second test.

^bThe relative standard error for these rates is 35%–50% and should be interpreted with caution.

^cThe relative standard error for these rates is >50% and should be interpreted with caution.

Within the 119 nested case–control group B converters, 100 patients received LTBI diagnoses, 57% initiated treatment, and 65% completed treatment (Supplementary Figure 1). Among group B converters, 20% (24/119) had documented travel between tests, and 96% (23/24) occurred in East or Southeast Asia (Supplementary Figure 2). Among group B non-converters, 13% (39/311) had documented travel between tests; 87% (34/39) indicated a travel destination, with 82% (28/34) occurring in East or Southeast Asia. Overall, >90% of travel with documented destination occurred within countries with high or medium TB prevalence [12]; the most frequently visited countries or regions included China, Vietnam, and Hong Kong. Travel duration was recorded for 41% (26/63) of patients with documented travel; duration ranged from 21 days to 1 year with a median of 1 month. After adjusting for age, sex, SRO residence, and secular trends, patients with documented travel had a 1.95-fold (95% confidence interval [CI] 1.07-3.57) increased odds of TB test conversion compared with patients without documented travel (Table 4). When excluding 56 patients who were retested during the SARS-CoV-2 pandemic, the adjusted odds ratio was 2.15 (95% CI 1.10-4.21, n = 372).

Table 4.

Sensitivity Analysis of Estimated Association Between Travel Exposure Between Tests and Test Conversion

Model Name	Description	aOR (95% CI)	N
Model 1 (Final)	Final analysis with replacement non-converters included. All ineligible non-converters and ineligible converters and their matched non-converters excluded.	1.95 (1.07–3.57)	457
Model 2 (No pandemic)	Final model 1 with additional exclusion of risk sets that had a second eligible test occurring within the 2020–2022 SARS-CoV-2 pandemic years.	2.15 (1.10–4.21)	372
Model 3 (No replacement non-converters)	All ineligible non-converters and ineligible converters and their matched non-converters excluded. No replacement non-converters included in analysis.	1.87 (1.02–3.44)	452
Model 4 (Original NCC)	Analyses with original nested case–control group without any exclusion based on new ineligibility from chart review.	2.36 (1.37–4.06)	540

Abbreviations: aOR, adjusted odds ratio; CI, confidence interval; NCC, nested case–control study; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

DISCUSSION

In a US population at higher risk for TB infection due to Asian race and nativity, overall TB test conversion incidence was low. Interferon-gamma release assay conversions occurred less frequently, and TST conversions occurred more frequently than in prior published estimates in lower-TB-prevalence settings. International travel doubled the odds of TB test conversion. Several patients had incident TB disease diagnosed during the study period after their test conversion. Among those tested with IGRA, incident TB disease occurred exclusively among high-positive IGRA converters.

In our analysis of a primarily Asian American community health center patient population, more than half of serial testing for TB infection was performed in children, consistent with prior work in which children were more likely to complete annual TB screening and received appropriate TB testing, compared with adults [6]. The proportion of patients with IGRA conversions (3.2%) was low compared with previously published estimates of serial TB testing performed in US healthcare workers with an average risk of TB exposure (6.1%); in contrast, the proportion of patients with TST conversions in our study (2.9%) was higher than previously described in healthcare workers (0.9%) [13]. The TST conversions in our study had 3 age-related peaks: in older children, adults age 35–44, and adults age 65–84. Given the lack of specificity of TSTs, which contain antigens shared with the BCG vaccine and non-tuberculous mycobacteria, and the likelihood of BCG vaccination for many of our patients in home countries in Asia, it was difficult to interpret the age-based trends in TST conversions observed in our study. Although “boosted” TST reactions can occur in the setting of serial testing of patients with remote TB exposure or BCG vaccination [14], BCG-related immunity wanes with age, and the biennial or annual cadence of TST testing makes boosting an unlikely explanation for the higher proportions of TST conversions in older children and adults [15–17]. In contrast, IGRA testing is not impacted by these factors. Our observation of an age-related increase in IGRA conversions until age 85 was more consistent with previously published trends from medium- or high-burden TB settings and could reflect higher cumulative incidence of TB exposure as patients’ age.

Previous literature indicated that low-positive IGRA tests were poor predictors of developing TB disease. Serial testing in US healthcare workers, which included more than a third who were at very low risk of TB exposure due to rare or no patient care duties, demonstrated that among people with QFT conversions and quantitative values of <0.7 IU/mL, more than half reverted to negative when retested [13]. In a recent meta-analysis, IGRA conversions or reversions were frequent and often transient, with pooled frequency of IGRA conversion estimated at 7.3% (95% CI 6.1%–8.5%) and the frequency of reversion estimated at 22.8% (95% CI 20.1%–25.7%); low-positive quantitative IGRA values from 0.35 to 0.7 IU/mL were associated with increased risk of conversion or reversion [18].

Among routinely tested IGRA converters in our study, reversions to negative occurred in almost 1 in 5 patients; however, some IGRA conversions were associated with incident TB disease. Estimated TB disease rates in our routine testing cohort were unstable due to small numbers. However, the 5-year rate of TB disease was comparable to the 5-year TB progression rate of 3.4/1000 py published by Menzies et al [19]. Our relatively lower estimates of progression to TB disease in the 1- and 2-year groups may indicate that we captured some patients with remote infection who appeared newly positive, rather than true incident infection. Although we hoped to assess the risk of progression to TB disease stratified by quantitative IGRA results, we were limited by small numbers. However, notably among those with IGRA conversions and quantitative values available, incident TB disease occurred exclusively among patients with high-positive IGRA results.

Encouragingly, among test converters who underwent chart review for the nested case–control study, treatment was prescribed for nearly 60% of patients, which was higher than the treatment rate for the health center's general population during a similar time period [6]. Prior measurements of the LTBI care cascade in lower-TB-prevalence settings have yielded widely varying estimates of eligible patients started on LTBI therapy, ranging from 7% to >70% [6, 20–24]. Meta-analysis of the LTBI care cascade has indicated attrition throughout the pathway, with significant drop-offs at medical evaluation completion and recommendation for treatment [25].

Our analysis suggests that international travel may be associated with an increase in risk of TB infection. We tested a variety of models and exclusion criteria to estimate this association; all models estimated an approximate 2-fold increase in odds of TB test conversion associated with international travel. In low-TB-prevalence countries, some studies suggest a small but measurable risk of TB infection, measured by IGRA, when travelers return from a country with higher-TB prevalence, while others suggest this risk is concentrated in certain types of travel, including healthcare work [26–29]. In a prospective study in the Netherlands where travelers to higher-TB-prevalence countries received pre- and posttravel TB testing, travel resulted in an IGRA conversion rate of 0.85 per 1000 person-months and a TST conversion rate of 4.26 per 1000 person-months, with a single conversion leading to TB disease in a patient who had worked in a healthcare setting [30]. In another study in the United Kingdom, among immigrants with a TB diagnosis more than 2 years after immigration, more than half reported recent travel to a country with higher-TB prevalence [5]. Our study contributes to an evolving body of literature that indicates travel to countries with higher prevalence of TB may be a clinically relevant risk factor for TB infection. Although our study was performed in a predominantly Asian population, we believe this finding is generalizable to other immigrant populations who travel to home countries in medium- and high-TB-prevalence regions.

We are limited by the retrospective nature of our analysis. Although we made efforts to control for TB exposure risks by defining a “routine tester” population and performing chart review, misclassification of travel as a reason for serial testing could have impacted results. We know that risk-based testing for TB infection at NEMS was low, particularly during the first half of the study period; this in part reflects the fact that USPSTF Recommendations on TB Screening were not published until 2016, with California issuing state-specific guidance in 2018 [6, 31, 32]. However, categorization of reasons for serial testing relied upon documentation in provider notes and was non-uniform, with a high proportion missing information about duration of travel, and no routinely collected information about type of employment. An additional consideration is sparse treatment completion data, which limited our ability to confirm whether LTBI treatment occurred between tests among patients who reverted from positive to negative. Finally, we caution against drawing strong conclusions on pregnancy from this study; the determination of pregnancy periods through EHR is complex, and limited data were available [33].

Among a patient population of primarily Asian immigrants and their US-born children in a low-TB-prevalence country, the incidence of TB test conversion was low and frequently resulted in subsequent reversion. Travel, primarily to countries in Asia, increased odds of test conversion by nearly 2-fold. Incident TB disease was diagnosed in several patients following their TB test conversions; for those tested with IGRAs who had quantitative results available, incident TB disease occurred only among persons with high-positive results. Our results suggest that clinically significant IGRA conversions in low-TB-prevalence countries are rare and that international travel may increase the risk of TB test conversion. Future work with prospectively collected data and a larger sample size could confirm the relationship between travel and TB test conversion in low-TB-prevalence settings and strengthen the argument for incorporating travel into risk-based testing, particularly for those who travel frequently to home countries. Our results also highlight the importance of collecting EHR data on travel and LTBI treatment completion in order to appropriately care for patients and prevent future cases of TB disease.

Supplementary Data

Supplementary materials are available at Open Forum Infectious Diseases online. Consisting of data provided by the authors to benefit the reader, the posted materials are not copyedited and are the sole responsibility of the authors, so questions or comments should be addressed to the corresponding author.