Abstract
The laboratory diagnosis of latent tuberculosis infection (LTBI) is mainly performed with interferon gamma release assays (IGRAs). We compared the performance of a new enzyme-linked immunosorbent assay (ELISA)-based IGRA, the Standard E TB-Feron ELISA (TBF; SD Biosensor, Gyeonggi-do, Republic of Korea), with that of a widely used assay, the QuantiFERON-TB Gold In-Tube assay (QFT-GIT; Qiagen, Hilden, Germany), in a population of 425 health care workers (HCWs). All HCWs were screened by both assays per the manufacturers' protocols and in a cross-manner, where tube sets from one assay were used with the alternative ELISA. The results were compared both qualitatively and quantitatively. TBF and QFT-GIT identified 11.3% (48/425) and 12.9% (55/425) of the positive samples, respectively. TBF demonstrated 81.6% positive and 97.4% negative percent agreement with QFT-GIT, with a Cohen's kappa value of 0.78 (strong agreement). Discordant results were detected in 20 subjects (4.3%): 13 samples (65.0%) were TBF negative and QFT-GIT positive, 6 samples (30.0%) were TBF positive and QFT-GIT negative, and 1 sample provided TBF and QFT-GIT indeterminate/negative results. We observed a statistically significant degree of correlation between the interferon gamma reactivity between the two assays (Spearman's rho [r(s) ] value = 0.551, P < 0.01) and between standard assays and cross-manner tests (r(s) value range, 0.449 to 0.816; P < 0.01 for all combinations). Cross-manner tests also revealed that the ELISA kit of TBF provided higher values for the tube containing the tuberculosis (TB) antigen and the negative-control tube than the ELISA of QFT-GIT under the same conditions (P < 0.01), although these differences disappeared when the value for the negative-control tube was subtracted from that for the TB antigen tube. TBF showed a comparable and acceptable clinical performance in detecting LTBI compared to QFT-GIT. TBF represents a useful alternative tool as an ELISA-based IGRA, especially for large-scale screening for LTBI in HCWs.