Search CDDW Abstracts 2012
Return to Table of Contents
ASSESSING THE PERFORMANCE OF INTERFERON-GAMMA RELEASE ASSAYS IN INFLAMMATORY BOWEL DISEASE: A SYSTEMATIC REVIEW AND META-ANALYSIS
N Shahidi1, Y Fu1, H Qian2, B Bressler11Department of Medicine, Division of Gastroenterology; 2Centre for Health Evaluation and Outcome Sciences, University of British Columbia, Vancouver, BC
Aims: Current guidelines mandate screening for latent tuberculosis infection (LTBI) prior to commencing anti-tumor necrosis factor (anti-TNF) therapy. However, many patients are already taking immunosuppressive therapy (IST), which can affect current diagnostic tests, such as the tuberculin skin test (TST). Due to the recent introduction of the interferon-gamma release assays (IGRA), we sought out to assess their ability to detect LTBI in patients with inflammatory bowel disease (IBD) and the impact of IST on these new tests.
Methods: MEDLINE and EMBASE, were searched (up to June 2011) to identify studies evaluating the performance of three IGRAs (QuantiFERON-TB Gold (GFT-2G), QuantiFERON-TB Gold In-Tube (GFT-3G) and T-SPOT.TB) in individuals with IBD. A hierarchy of outcomes for the evaluation of IGRAs was used to facilitate data extraction. Forest plots and pooled estimates using random effects models were created where applicable. For pooled estimates, QFT-2G and QFT-3G were considered equivalent
Results: 9 unique study populations, encompassing 1309 patients with IBD were included for analysis. The pooled concordance between the TST and QFT-2G/QFT-3G was 85% (95% CI 77% to 90%) in comparison to the concordance of the TST and TSPOT.TB which was 72% (95% CI 64% to 78%). All studies assessing percent agreement reported a greater proportion of IGRA-/TST+ results compared to IGRA+/TST- results. The pooled percent of indeterminate results was 5% (95% CI 2% to 9%) for QFT-2G/QFT-3G. TSPOT.TB showed similar results. IST significantly influenced both positive QFT-2G/QFT-3G results (pooled OR 0.37; 95% CI 0.16 to 0.87) and positive TST results (pooled OR 0.28; 95% CI 0.10 to 0.80) (both p=0.02). The negative impact of IST continued throughout sub-analyses concerning almost all forms of IST.
Conclusions: Our results suggest that while it remains difficult to determine superiority between the IGRAs and the TST in identifying LTBI in IBD, both are negatively affected by IST. Therefore, current guidelines which propose screening before anti-TNF therapy may want to consider suggesting screening prior to other forms of IST as well.