Comparison of LIAISON QuantiFERON-TB Gold Plus with QuantiFERON-TB Gold Plus

With the large global burden of latent tuberculosis infection (LTBI), screening for LTBI for various reasons has been widely used, including the low-prevalence settings in which targeted testing is the standard practice (1, 2). Interferon-gamma release assays (IGRAs) are usually preferred over tuberculin skin test given the limitations of the latter (3). Several versions of IGRAs have been introduced to the global market, each time with an improvement including performance characteristics and laboratory operations (4). We previously published an operational feasibility study using the latest version of IGRAs that is commercially available, LIAISON QuantiFERON-TB Gold Plus (DiaSorin Inc.) (LIAISON QFT-Plus) (5). As a sequel to our previous study, we set out to compare LIAISON QFT-Plus with QFT-Plus, including method comparison, intra- and inter-precision and cutoff verification in comparison with the previously used reference method, QuantiFERON-TB Gold Plus (Qiagen) (QFT-Plus). LIAISON QFT-Plus is based on chemiluminescence immunoassay whereas QFT-Plus is based on enzyme immunoassay, and our laboratory did the test on DSX (Dynex technologies) batch analyzers. To this end, 190 randomly-selected, de-identified residual plasma samples were used for the comparisons. The samples were procured based on manufacturer’s instructions and within the established stability requirements in the lab (typically kept at ≤–20°C up to 28 days). Of these stored samples, 97, 23, and 70 had initial negative, indeterminate, and positive results, respectively. For the precision and cutoff verification studies, we compared both TB1 and TB2 result components for which we arbitrarily chose low (0.35 to 1.0 IU/mL) and high (>1.0 IU/mL) levels (one sample from each). For the cutoff verification, a sample was used with initial values within 20% of the positivity cutoff (0.35 IU/mL) and tested 10 times in 1 run.