The CDC recommends screening HIV-infected patients for latent tuberculosis infection (LTBI) annually with the tuberculin skin test (TST) or an interferon gamma release assay (IGRA). Though IGRAs are more specific and operationally advantageous, recent data suggests they are not reliable in HIV-infected people because of frequent indeterminate results and spontaneous reversions. We measured the frequency of LTBI, spontaneous IGRA reversions, and LTBI treatment.
We performed a retrospective review of IGRA and TST results at a large New York City HIV clinic from 01/2011 to 04/2014. We included those 18 years or older with HIV who were screened for LTBI with no history of LTBI or active TB. We collected demographic data, HIV parameters (e.g. CD4 count, plasma HIV RNA), and management of LTBI.
1745 patients were screened for LTBI with either IGRA or TST. The median age was 49 (52-56) years old, 74% were male. The median CD4 count was 499 (326-711), 67.5% had an undetectable plasma HIV RNA. 1321 (76%) had at least one IGRA, 1215 (70%) had at least one TST, and 791 (45%) had both. Among the 1321 patients tested with IGRA, 109 (8.3%) were positive, 67 (5.1%) had an indeterminate result, and 1145 (87%) were consistently negative. Among 1215 patients tested with the TST, 19 (1.6%) had a positive result.
Among the 109 patients with a positive IGRA, 85 (78%) had a prior negative TST. 72 (72%) had repeat IGRA without interim LTBI treatment: 14 were positive and 58 were negative suggesting a spontaneous reversion rate of at least 58/109(53%). Of 67 patients with an initial indeterminate IGRA, 50 (75%) had repeat testing: 42(84%) were negative, and 8(16%) had persistent indeterminate IGRA. None had a positive IGRA on follow up testing. 27 of 109 patients with a positive IGRA (25%) underwent treatment for LTBI as compared to 15 of 19 (79%) of those with a positive TST.
Conclusion: A newly positive IGRA result should be interpreted with caution in HIV-infected patients from low-incidence TB settings as spontaneous reversions are seen in at least 50% of patients. Further data are needed to clarify the role of confirmatory testing after a positive IGRA prior to initiating LTBI treatment.
K. C. Ma,
T. Wilkin, GSK/Viiv: Consultant , Consulting fee
BMS: Investigator , Grant recipient
Gilead: Investigator , Grant recipient
X. Wu, None
A. Li, None
H. Singh, None