Comparison of Tuberculin Skin Testing and Interferon-γ Release Assays in Predicting Tuberculosis Disease.

Importance: Elimination of tuberculosis (TB) disease in the US hinges on the ability of tests to detect individual risk of developing disease to inform prevention. The relative performance of 3 available TB tests-the tuberculin skin test (TST) and 2 interferon-γ release assays (IGRAs; QuantiFERON-TB Gold In-Tube [QFT-GIT] and SPOT.TB [TSPOT])-in predicting TB disease development in the US remains unknown. Objective: To compare the performance of the TST with the QFT-GIT and TSPOT IGRAs in predicting TB disease in high-risk populations. Design, Setting, and Participants: This prospective diagnostic study included participants at high risk of TB infection (TBI) or progression to TB disease at 10 US sites between 2012 and 2020. Participants of any age who had close contact with a case patient with infectious TB, were born in a country with medium or high TB incidence, had traveled recently to a high-incidence country, were living with HIV infection, or were from a population with a high local prevalence were enrolled from July 12, 2012, through May 5, 2017. Participants were assessed for 2 years after enrollment and through registry matches until the study end date (November 15, 2020). Data analysis was performed in June 2023. Exposures: At enrollment, participants were concurrently tested with 2 IGRAs (QFT-GIT from Qiagen and TSPOT from Oxford Immunotec) and the TST. Participants were classified as case patients with incident TB disease when diagnosed more than 30 days from enrollment. Main Outcomes and Measures: Estimated positive predictive value (PPV) ratios from generalized estimating equation models were used to compare test performance in predicting incident TB. Incremental changes in PPV were estimated to determine whether predictive performance significantly improved with the addition of a second test. Case patients with prevalent TB were examined in sensitivity analysis. Results: A total of 22 020 eligible participants were included in this study. Their median age was 32 (range, 0-102) years, more than half (51.2%) were male, and the median follow-up was 6.4 (range, 0.2-8.3) years. Most participants (82.0%) were born outside the US, and 9.6% were close contacts. Tuberculosis disease was identified in 129 case patients (0.6%): 42 (0.2%) had incident TB and 87 (0.4%) had prevalent TB. The TSPOT and QFT-GIT assays performed significantly better than the TST (PPV ratio, 1.65 [95% CI, 1.35-2.02] and 1.47 [95% CI, 1.22-1.77], respectively). The incremental gain in PPV, given a positive TST result, was statistically significant for positive QFT-GIT and TSPOT results (1.64 [95% CI, 1.40-1.93] and 1.94 [95% CI, 1.65-2.27], respectively). Conclusions and Relevance: In this diagnostic study assessing predictive value, IGRAs demonstrated superior performance for predicting incident TB compared with the TST. Interferon-γ release assays provided a statistically significant incremental improvement in PPV when a positive TST result was known. These findings suggest that IGRA performance may enhance decisions to treat TBI and prevent TB.

Evaluation of the Latent Tuberculosis Care Cascade Among Public Health Clinics in the United States.

BACKGROUND: Tuberculosis (TB) elimination within the United States will require scaling up TB preventive services. Many public health departments offer care for latent tuberculosis infection (LTBI), although gaps in the LTBI care cascade are not well quantified. An understanding of these gaps will be required to design targeted public health interventions. METHODS: We conducted a cohort study through the Tuberculosis Epidemiologic Studies Consortium (TBESC) within 15 local health department (LHD) TB clinics across the United States. Data were abstracted on individuals receiving LTBI care during 2016-2017 through chart review. Our primary objective was to quantify the LTBI care cascade, beginning with LTBI testing and extending through treatment completion. RESULTS: Among 23 885 participants tested by LHDs, 46% (11 009) were male with a median age of 31 (interquartile range [IQR] 20-46). A median of 35% of participants were US-born at each site (IQR 11-78). Overall, 16 689 (70%) received a tuberculin skin test (TST), 6993 (29%) received a Quantiferon (QFT), and 1934 (8%) received a T-SPOT.TB; 5% (1190) had more than one test. Among those tested, 2877 (12%) had at least one positive test result (3% among US-born, and 23% among non-US-born, P < .01). Of 2515 (11%) of the total participants diagnosed with LTBI, 1073 (42%) initiated therapy, of whom 817 (76%) completed treatment (32% of those with LTBI diagnosis). CONCLUSIONS: Significant gaps were identified along the LTBI care cascade, with less than half of individuals diagnosed with LTBI initiating therapy. Further research is needed to better characterize the factors impeding LTBI diagnosis, treatment initiation, and treatment completion.

Higher Rates of Tuberculosis Among Class B1 Filipino Immigrants to Hawaii Compared to Nationwide, 2010-2014.

BACKGROUND: Immigrants to the United States from countries with a high burden of tuberculosis (TB) who have abnormal chest radiographs but negative sputum cultures during pre-immigration screening (TB Class B1) have a high risk of being diagnosed with TB disease within 1 year of arrival. METHODS: Using 2010-2014 national surveillance data, we compared proportions of Class B1 Filipino immigrants who received a diagnosis of TB disease within 1 year of arrival to Hawaii to proportions in other U.S. states (not including Hawaii) using chi-squared tests. RESULTS: In Hawaii, 40/1190 (3.4%) of Class B1 Filipino immigrants to Hawaii received a diagnosis of TB disease within 1 year of arrival compared with 220/16,035 (1.4%) nationwide (P < .01). CONCLUSIONS: During 2010-2014, the percentage of recent Class B1 Filipino immigrants in Hawaii with TB disease diagnosed within 1 year of arrival was over twice that as nationwide.