Programmatic Impact of QuantiFERON-TB Gold In-Tube Implementation on Latent Tuberculosis Diagnosis and Treatment in a Public Health Clinic

Background: QuantiFERON-TB Gold In-Tube (QFT-GIT) is considered an alternative to the tuberculin skin test (TST) for the diagnosis of tuberculosis (TB) infection, but the programmatic impact of QFT-GIT implementation is largely unknown. In March, 2010, the Baltimore City Health Department (BCHD) introduced routine QFT-GIT testing for individuals referred to the TB program for suspected latent TB infection (LTBI). Design: Retrospective study comparing LTBI diagnosis and treatment during the 13 months before and after QFT-GIT implementation at the BCHD TB clinic. Results: 607 and 750 individuals were referred by community-providers for suspected LTBI in the pre- and post-QFT-GIT periods, respectively. Most individuals in the pre- and post-QFT-GIT periods were referred on the basis of a positive TST (597/607 [98%] vs. 690/750 [92%], respectively) and were foreign-born (363/607[59%] vs. 507/750[68%], respectively). BCHD performed QFT-GIT testing for 375/543 (69%) eligible individuals in the post-QFT-GIT period, of which 185 (49%) were positive, 178 (47%) were negative, 1 (0.25%) was indeterminate, and 11 (3%) did not yield results. Concordance of QFT-GIT with TST was low (183/352[52%]). Foreign-born individuals had higher proportions of QFT-GIT positivity (57%) than US-born individuals (36%; AOR 3.3 [95%CI 1.7–6.2]). Significantly fewer individuals received a final diagnosis of LTBI in the post-QFT-GIT period (397/567 [70%]) compared to the pre-QFT-GIT period (445/452 [98%], p,0.001). In the post-QFT-GIT period, onl

Concordance of TST and QFT-GIT results among referred individuals that came to BCHD for LTBI evaluation and had both tests performed.

†<p>Overall, 352 individuals had a TST and interpretable QFT-GIT result available. There was an overall concordance of 52.3%.</p>*<p>8 individuals with negative TST results were referred and evaluated by BCHD. 4 individuals with B-waivers had negative TST, but were referred due to an abnormal CXR; 4 individuals had both TST and QFT-GIT performed by referral source.</p

Characteristics of individuals referred to Baltimore City Health Department TB Clinic for evaluation of suspected <i>M. tuberculosis</i> infection, by study period.

<p>Abbreviations: SD, Standard Deviation. BCHD, Baltimore City Health Department.</p>*<p>Ethnicity data was based on referral documentation and/or initial evaluation at BCHD. P-value for global comparison of equality of proportions of ethnicities by χ² test.</p>†<p>HIV test results are available only for those that came to BCHD for evaluation. HIV status not available for those who did not complete an LTBI evaluation at BCHD.</p>**<p>Includes referrals from other local health departments in Maryland and other states, as well as employment TB testing conducted through other BCHD programs.</p

Factors associated with QFT-GIT test positivity among those tested at BCHD.

<p>Only individuals with QFT-GIT performed by BCHD are included. 11 individuals had blood drawn for QFT-GIT but did not have interpretable results due to insufficient blood volume during venipuncture, sample transportation issues, or processing error. There was 1 indeterminate result.</p><p>°p<0.001 for both univariate and multivariate analysis comparing foreign-born to US born individuals.</p><p>°° P = 0.042 comparing HIV positive to HIV negative individuals.</p>†<p>Referral source was omitted from multivariate regression model due to collinearity with birth country.</p>††<p>p = 0.001 comparing those referred from Refugee health services to those referred from primary care providers/other; p = 0.03 comparing those referred from local health departments to those referred from primary care providers/other.</p

Differences in LTBI diagnosis among referrals to BCHD between study periods and by QFT-GIT test status.

*<p>includes individuals that had QFT-GIT performed by referral source. 11/399 individuals in the post-QFT-GIT period had QFT-GIT drawn but no results available; there was 1 indeterminate result in the post-QFT-GIT-period.</p><p>°p<.001 comparing final diagnosis of LTBI between pre-QFT-GIT and post-QFT-GIT periods.</p><p>°°p = .827 for pre-QFT-GIT period comparing LTBI diagnosis between those with and without a QFT-GIT result; p<.001 in post-QFT-GIT period comparing LTBI diagnosis between those with and without QFT-GIT performed.</p>**<p>p = .81 comparing treatment initiation among those diagnosed with LTBI between pre-QFT-GIT and post-QFT-GIT periods; p = 0.690 comparing treatment initiation between those with and without QFT-GIT performed in the pre-QFT-GIT period; p = .349 comparing treatment intiation between those with and without QFT-GIT performed in the post-QFT-GIT period.</p>†<p>Analysis restricted to those who started an INH X 9 months regimen prior to Nov 30, 2010 or Rifampin X 4 months prior to March 30, 2011 to allow time for completion. p = .606 comparing overall treatment completion between pre-QFT-GIT period and post-QFT-GIT period. p = 0.101 comparing those with and without QFT-GIT performed in the post-QFT-GIT period; p = 0.70 comparing those with and without QFT-GIT in the pre-QFT-GIT period.</p