Diagnostic accuracy of IL-2 for the diagnosis of latent tuberculosis: a systematic review and meta-analysis

We conducted a systematic review and meta-analysis to evaluate the diagnostic potential of interleukin-2 (IL-2) as biomarkers for the diagnosis of latent tuberculosis. Related studies were identified through searches of PubMed, Embase, Web of Science, and complementary manual searches up to December 30, 2013. We used standard methods recommended for meta-analyses of diagnostic test evaluations. The analysis was based on a summary receiver operating characteristic (SROC) curve. Meta-regression analysis was used to assess the effects of some confounding factors on the results of the meta-analysis. The potential presence of publication bias was tested using the Deeks' funnel plots. The pooled estimates of IL-2 for latent tuberculosis infection (LTBI) diagnosis were as follows: sensitivity, 0.81 [95 % confidence interval (CI), 0.60 to 0.92]; specificity, 0.95 (95 % CI, 0.90 to 0.97); positive likelihood ratio (PLR), 15.2 (95 % CI, 8.1to 28.4); negative likelihood ratio (NLR), 0.20 (95 % CI, 0.09 to 0.47). We found that the SROC curve is positioned near the upper left corner of the curve and the area under the curve (AUC) was 0.96 (95 % CI, 0.94 to 0.98). In conclusion, according to the meta-analysis, IL-2 is a valid marker for the diagnosis of LTBI. When there is no definite gold standard for the diagnosis of LTBI, IL-2 release assay in addition to interferon-gamma release assays (IGRAs) can improve the ability of IGRAs to identify individuals with LTBI.