A Summary of Meeting Proceedings on Addressing Variability around the Cut Point in Serial Interferon-γ Release Assay Testing

Abstract

On June 13, 2012, a group of key stakeholders, leaders, and national experts on tuberculosis (TB), occupational health, and laboratory science met in Atlanta, Georgia, to focus national discussion on the higher than expected positive results occurring among low-risk, unexposed healthcare workers undergoing serial testing with interferon-γ release assays (IGRAs). The objectives of the meeting were to present the latest clinical and operational research findings on the topic, to discuss evaluation and treatment algorithms that are emerging in the absence of national guidance, and to develop a consensus on the action steps needed to assist programs and physicians in the interpretation of serial testing IGRA results. This report summarizes its proceedings.

Frequent conversion of tuberculosis screening tests during anti-tumour necrosis factor therapy in patients with rheumatic diseases

“…If stricter criteria for test conversion were applied, as has been proposed,8–10 then 15 patients (21%) would have been considered as converters. More specifically, TST conversion defined as a TST increase >6 mm above the baseline value to a diameter of >10 mm8 was seen in eight patients (11%), T-SPOT.TB conversion, defined as an increase from <6 spots/well at baseline to ≥9 spots/well,9 in five patients (7%), and QFT-GIT conversion, defined as an IFN-γ concentration (after specific TB antigen stimulation) of >0.7 IU/mL or even 1 IU/mL,9 10 in two (3%) patients.…”

Demographics and prevalence of positive QuantiFERON‐TB Gold In‐Tube test in renal transplant candidates

“…A QFT‐GIT value of ≥0.35 < 1 IU/mL (low/intermediate‐positive) has been associated with false positivity in college students and health care workers with low TB risk. A group of TB experts has recommended retesting health care workers with low TB risk and low/intermediate‐positive QFT‐GIT to detect possible false‐positive results . Whether this recommendation can be extrapolated to transplant candidates is unclear, as pre‐transplant patients with LTBI who are not treated are at significant risk for TB reactivation after SOT .…”

Childhood Tuberculosis

“…Most of these fluctuations, however, remain unexplained. Hence, well-controlled studies are needed to define the causes of individual variations in IFN-c response and to develop criteria to differentiate nonspecific variation from that associated with new or resolving infection [43,44].…”