Performance of the tuberculin skin test and interferon-γ release assay for detection of tuberculosis infection in immunocompromised patients in a BCG-vaccinated population

Abstract

BackgroundInterferon-γ release assay (IGRA) may improve diagnostic accuracy for latent tuberculosis infection (LTBI). This study compared the performance of the tuberculin skin test (TST) with that of IGRA for the diagnosis of LTBI in immunocompromised patients in an intermediate TB burden country where BCG vaccination is mandatory.MethodsWe conducted a retrospective observational study of patients given the TST and an IGRA, the QuantiFERON-TB Gold In-Tube (QFT-IT), at Severance Hospital, a tertiary hospital in South Korea, from December 2006 to May 2009.ResultsOf 211 patients who underwent TST and QFT-IT testing, 117 (55%) were classified as immunocompromised. Significantly fewer immunocompromised than immunocompetent patients had positive TST results (10.3% vs. 27.7%, p 0.001), whereas the percentage of positive QFT-IT results was comparable for both groups (21.4% vs. 25.5%). However, indeterminate QFT-IT results were more frequent in immunocompromised than immunocompetent patients (21.4% vs. 9.6%, p 0.021). Agreement between the TST and QFT-IT was fair for the immunocompromised group (κ = 0.38), but moderate agreement was observed for the immunocompetent group (κ = 0.57). Indeterminate QFT-IT results were associated with anaemia, lymphocytopenia, hypoproteinemia, and hypoalbuminemia.ConclusionIn immunocompromised patients, the QFT-IT may be more sensitive than the TST for detection of LTBI, but it resulted in a considerable proportion of indeterminate results. Therefore, both tests may maximise the efficacy of screening for LTBI in immunocompromised patients.

Significant Reduction in Rate of Indeterminate Results of the QuantiFERON-TB Gold In-Tube Test by Shortening Incubation Delay

“…In that study, highly advanced age, immunosuppressive treatment, lymphocytopenia (including CD4 ϩ lymphocytopenia), and hypoproteinemia could (12). In our study, based on the multivariate logistic regression analysis, taking immunosuppressive drugs, previously existing underlying diseases, bedridden status, and hypoalbuminemia were associated with increases in the frequency of indeterminate QFT-G IT test results.…”

“…Rates of indeterminate results of 5% to 40% for all participants and approximately 6% for health care workers have been reported (8-10). Rates of indeterminate results of 15.6% and 16.1% have been reported for two large tertiary care hospitals in South Korea (11,12). Considering the composition of the high-risk populations and the therapeutic approaches used at the hospital, the frequency of indeterminate results may vary depending on hospital conditions.…”

Evaluating Indeterminate Interferon‐γ–Release Assay Results in Patients With Chronic Inflammatory Diseases Receiving Immunosuppressive Therapy

“…This is evidenced in several studies looking at indeterminate tests as a function of lymphocytes. Kim et al found lymphocytopenia to be independently associated with indeterminate results (25). Similarly, a study looking at IGRA in patients with HIV found indeterminate results to correlate with CD4 counts ,200 cells/ml (22), further suggesting a strong correlation with depressed cell mediated immunity.…”

Immunological Diagnosis of Active and Latent TB

“…There are various conditions such as oncologic disease, HIV infection, anti-TNF-, corticoid or other immunomodulatory therapy, diabetes mellitus, renal failure or other immunocompromising conditions that are responsible for intermediate or false negative results (Schoepfer et al, 2008;Matulis et al, 2008;Kim et al, 2009). Particularly, the anti-TNF- treatment has increased recently, which hampers the activation of the innate immune responses, T cell mediated adaptive immune response and production of protective IFN-.…”