Analysis of Factors Lowering Sensitivity of Interferon-c Release Assay for Tuberculosis

Background: Imperfect sensitivity of interferon-c release assay (IGRA) is a potential problem to detect tuberculosis. We made a thorough investigation of the factors that can lead to false negativity of IGRA. Methods: We recruited 543 patients with new smear-positive pulmonary tuberculosis in Hanoi, Viet Nam. At diagnosis, peripheral blood was collected and IGRA (QuantiFERON-TB Gold In-Tube) was performed. Clinical and epidemiological information of the host and pathogen was collected. The test sensitivity was calculated and factors negatively influencing IGRA results were evaluated using a logistic regression model in 504 patients with culture-confirmed pulmonary tuberculosis. Results: The overall sensitivity of IGRA was 92.3 % (95 % CI, 89.6%–94.4%). The proportions of IGRA-negative and-indeterminate results were 4.8 % (95 % CI, 3.1%–7.0%) and 3.0 % (95 % CI, 1.7%–4.9%). Age increased by year, body mass index,16.0, HIV co-infection and the increased number of HLA-DRB1*0701 allele that patients bear showed significant associations with IGRA negativity (OR = 1.04 [95 % CI, 1.01–1.07], 5.42 [1.48–19.79], 6.38 [1.78–22.92] and 5.09 [2.31–11.22], respectively). HIV co-infection and the same HLA allele were also associated with indeterminate results (OR = 99.59 [95 % CI, 15.58–625.61] and 4.25 [1.27–14.16])