UC San Diego

Background

Increased risk of progression from latent tuberculosis infection (LTBI) to tuberculosis (TB) disease among people living with human immunodeficiency virus (HIV; PLWH) prioritizes them for LTBI testing and treatment. Studies comparing the performance of interferon gamma release assays (IGRAs) and the tuberculin skin test (TST) among PLWH are lacking.

Methods

We used Bayesian latent class analysis to estimate the prevalence of LTBI and diagnostic characteristics of the TST, QuantiFERON Gold In-Tube (QFT), and T.SPOT-TB (TSPOT) among a prospective, multicenter cohort of US-born PLWH ≥5 years old with valid results for all 3 LTBI tests using standard US cutoffs (≥5 mm TST, ≥0.35 IU/mL QFT, ≥8 spots TSPOT). We also explored the performance of varying LTBI test cutoffs.

Results

Among 1510 PLWH (median CD4+ count 532 cells/mm3), estimated LTBI prevalence was 4.7%. TSPOT was significantly more specific (99.7%) and had a significantly higher positive predictive value (90.0%, PPV) than QFT (96.5% specificity, 50.7% PPV) and TST (96.8% specificity, 45.4% PPV). QFT was significantly more sensitive (72.2%) than TST (54.2%) and TSPOT (51.9%); negative predictive value of all tests was high (TST 97.7%, QFT 98.6%, TSPOT 97.6%). Even at the highest cutoffs evaluated (15 mm TST, ≥1.00 IU/mL QFT, ≥8 spots TSPOT), TST and QFT specificity was significantly lower than TSPOT.

Conclusions

LTBI prevalence among this cohort of US-born PLWH was low compared to non-US born persons. TSPOT's higher PPV may make it preferable for testing US-born PLWH at low risk for TB exposure and with high CD4+ counts.