CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

Table: Performance of WHO tool Conclusions: In this setting the WHO 4-symptom tool performs extremely well for the purpose for which it was designed, to rule out TB, both amongst ART experienced and ART naïve individuals. However the low positive predictive value necessitates clear guidance on further evaluation of those who screen positive, in order to rationalise further investigation and avoid burdening health care systems in resource-limited settings. 824 Xpert MTB/RIF Versus AFB Smear to Determine Respiratory Isolation of US TB Suspects Anne Luetkemeyer 1 ; Cynthia Firnhaber 7 ; Michelle Kendall 2 ; XingyeWu 2 ; Debra Benator 3 ; Gerald Mazurek 4 ; Diane Havlir 1 ; Beatriz Grinsztejn 5 ; David Alland 6 on behalf of the ACTG A5295/TBTC 34 StudyTeams 1 San Francisco General Hospital, University of California San Francisco, San Francisco, CA, US; 2 Harvard School of Public Health, Center for Biostatistics in AIDS Research, Boston, MA, US; 3 Washington DC Veterans Affairs Medical Center, Washington, DC, US; 4 US Centers for Disease Control and Prevention, Atlanta, GA, US; 5 Instituto de Pesquisa Clinica Evandro Chagas, Rio de Janiero, Brazil; 6 Rutgers New Jersey Medical School, Newark, NJ, US; 7 University of Witswatersrand, Johannesburg, South Africa; 8 ACTG A5295/TBTC 34 Study Teams, N/a, MA, US Background: U.S. guidelines recommend respiratory isolation during evaluation of suspected pulmonary tuberculosis (TB) until demonstration of serial negative acidfast bacilli(AFB) sputa. We evaluated the strategies of 1 vs. 2 rapid nucleic acid GeneXpert MTB/RIF(Xpert) tests in comparison to AFB smear for the initial diagnostic evaluation, including in persons with HIV, for whom prompt TB diagnosis is a priority. Methods: Patients undergoing pulmonary TB evaluation had 2 sputa tested by Xpert(G4 cartridges) and compared to 2 sputum AFB smears; a subset had 3 AFB smears available. TB culture status was determined by 2 sputa samples, each cultured on both liquid and solid media. Those with M. tuberculosis on any of 4 cultures were classified as TB+. All had HIV testing. Exact McNemar’s test was used for comparisons. Results: 633 participants had 2 AFB smear results: median age 49 years, 69%male, 78% inpatient at time of evaluation, 38% HIV+. 91(14%) were TB+; 10(11%) of TB+ were HIV+. A subset of 361(57%) had 3 AFB smears. The initial Xpert identified 75 of 88 (85.2%) TB+ cases, compared to 69.3% for 2 AFB smears (p=0.001) (Table). Two Xperts identified 82/90 (91.1%)TB+ cases. Initial Xpert identified 59/61(96.7%) AFB+/TB+ and two Xperts identified all 62 AFB+/TB+. For the subset with 3 AFB, 1 Xpert and 2 Xperts identified 41/50 (82.0%) and 46/52 (88.5%) of TB+ cases compared to 60.4% for 3 AFB smears, and 1 Xpert and 2 Xperts identified 30/31 (96.8%) and 32/32 (100%) of AFB+/TB+, respectively. Specificity was 98.7% for the first Xpert and 98.4% for 2 Xperts, compared to 94.8% for 3 AFB smears (p =0.008 and 0.019, respectively). Of 18 AFB+/TB-, both 1 and 2 Xperts had 1 false positive result. Of 524 AFB-/TB-, 1 Xpert yielded 3 false positive results; 2 Xpert had 5. The negative predictive value(NPV) of 1 Xpert was 97.6%, NPV of 2 Xperts 98.5%, compared to the NPV of 2 smears of 94.8%(14% TB prevalence). The NPV of 3 AFB was 93.3%(4% TB prevalence). 1 Xpert had similar performance (p>0.05) in HIV+ vs. HIV- with sensitivity 87.5% vs. 85.0% and specificity 99.6% vs. 99.0%.

Poster Abstracts

Table: Comparison of Xpert vs. AFB for the initial TB evaluation in 91 culture confirmed TB cases Conclusions: A strategy of 2 Xperts missed no AFB+/TB+ patients, identifying all TB patients requiring respiratory isolation on the basis of AFB smear positive sputum. 1 and 2 Xperts were each significantly more sensitive and specific than 3 AFB smears for identifying culture-positive patients. These data support consideration of a 2 Xpert strategy to discontinue respiratory isolation of U.S.TB suspects, regardless of HIV status.

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CROI 2015