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

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

Flow diagram of Xpert and MGIT testing results.

<p>Flow diagram of Xpert and MGIT testing results.</p

Performance characteristics of the Xpert MTB/RIF test stratified by participant TB treatment status, using MGIT culture as the reference standard^a.

<p>Abbreviations: CI, confidence interval; MGIT, Mycobacteria Growth Indicator Tube; PPV, positive predictive value; NPV, negative predictive value.</p>a<p>Excluded from the analyses were 249 specimens that were contaminated in MGIT culture, 23 specimens that had a final result of failed on Xpert MTB/RIF testing, and 2 specimens from participants for whom data on TB treatment status were missing.</p>b<p>four participants who reported not being on current TB treatment but did not know if they had ever been on TB treatment were coded as “no current or prior TB treatment”.</p

Performance characteristics of the Xpert MTB/RIF test overall, and stratified by smear microscopy status, using MGIT culture as the reference standard.

<p>Abbreviations: CI, confidence interval; MGIT, Mycobacteria Growth Indicator Tube;</p><p>PPV, positive predictive value; NPV, negative predictive value.</p>a<p>Excluded from the analyses were 249 specimens that were contaminated in MGIT culture and 23 specimens that had a final result of failed on Xpert MTB/RIF testing.</p>b<p>sensitivity of smear microscopy for detection of MTB, using MGIT as reference standard, was 33/187 (17.6%, [95%CI 12.5, 23.9]) vs. Xpert sensitivity of 62.6% overall (p≤0.001).</p>c<p>These 54 specimens were culture-negative for <i>M. tuberculosis</i>. For 11/54, a non-tuberculous mycobacterium was isolated from culture. For 43/54 the culture was negative for any mycobacterial growth; among these 43 specimens, 32 were smear grade scanty.</p

Baseline characteristics of 6893 study participants.

<p>Abbreviation: IQR, interquartile range.</p>a<p>of these, 2613 reported never having had an HIV test, 122 had an HIV test but were not willing to disclose results, and 2 had missing data.</p>b<p>on treatment for active TB when the study sputum specimen was obtained.</p>c<p>prior treatment for active TB but not on TB treatment when the study sputum specimen was obtained.</p

Results for MGIT culture and Xpert MTB/RIF for 6893 sputum specimens.

*<p>p<0.001 for comparison of proportions of contaminated MGIT cultures (249/6893 [3.6%]) vs. invalid Xpert tests (23/6893 [0.3%]).</p

Diagnostic test costs, per specimen tested and for a testing program including 7000 sputum specimens.

<p>Abbreviations: MGIT, Mycobacterial Growth Indicator Tube; DST: drug susceptibility testing using the MGIT SIRE system.</p>a<p>includes the cost of sputum decontamination ($2.35/sputum specimen).</p>b<p>does not include the cost of sputum decontamination.</p>c<p>unit cost of Xpert MTB/RIF cartridges was$16.80.</p>d<p>incorporates the assumption that DST is performed for the 2.7% of specimens with growth of <i>M. tuberculosis</i> in culture.</p