Selected RD1 Peptides for Active Tuberculosis Diagnosis: Comparison of a Gamma Interferon Whole-Blood Enzyme-Linked Immunosorbent Assay and an Enzyme-Linked Immunospot Assay

Abstract

We recently set up a gamma interferon (IFN-␥) enzyme-linked immunospot assay (ELISPOT), using selected early secreted antigenic target 6 (ESAT-6) peptides, that appears specific for active tuberculosis (A-TB). However, ELISPOT is difficult to automate. Thus, the objective of this study was to determine if the same selected peptides may be used in a technique more suitable for routine work in clinical laboratories, such as whole-blood enzyme-linked immunosorbent assay (WBE). For this purpose, 27 patients with A-TB and 41 control patients were enrolled. Our WBE, using the already described selected peptides from ESAT-6 plus three new ones from culture filtrate protein 10, was performed, and data were compared with those obtained by ELISPOT. Using our selected peptides, IFN-␥ production, evaluated by both WBE and ELISPOT, was significantly higher in patients with A-TB than in controls (P < 0.0001). Statistical analysis showed a good correlation between the results obtained by WBE and ELISPOT (r ‫؍‬ 0.80, P < 0.001). To substantiate our data, we compared our WBE results with those obtained by QuantiFERON-TB Gold, a whole-blood assay based on region of difference 1 (RD1) overlapping peptides approved for TB infection diagnosis. We observed a slightly higher sensitivity with QuantiFERON-TB Gold than with our WBE (89% versus 81%); however, our test provided a better specificity result (90% versus 68%). In conclusion, results obtained by WBE based on selected RD1 peptides significantly correlate with those generated by ELISPOT. Moreover, our assay appears more specific for A-TB diagnosis than QuantiFERON-TB Gold, and thus it may represent a complementary tool for A-TB diagnosis for routine use in clinical laboratories.

Interferon-γ release assays for the diagnosis of latentMycobacterium tuberculosisinfection: a systematic review and meta-analysis

“…In nine of these, TST positivity was significantly associated with BCG vaccination as an independent predictor in multivariate analysis [47,50,55,62,67,71,72,74,77] with odd ratios ranging between 3.8 (95% CI 1.0-13.9) [50] [35] GOLETTI [36] JAFARI [37] JAFARI [38] KAMPMANN [39] KANG [40] LEE [41] MARKOVA [42] WANG [43] DETJEN [26] DHEDA [34] GOLETTI [36] KAMPMANN [39] KANG [40] MARKOVA [42] odds for test positivity with M. tuberculosis exposure gradients, or using chest radiography lesions as a surrogate of prior exposure, the IGRAs associated better with exposure than the TST, irrespective of the setting's disease burden. Furthermore, there was generally a poor agreement between IGRAs and TST results (for k statistics, see table 3).…”

“…NPV in patients with active tuberculosis 18 articles satisfied our inclusion criteria for evaluating the NPV; 13 assessed the NPV among confirmed tuberculosis cases [22,26,[34][35][36][37][38][39][40][41][42][43][44] and six assessed the prospective outcome in IGRA-negative individuals after an average of 2 yrs [19-22, 45, 46]. Among the studies in which the NPV was evaluated in patients with confirmed tuberculosis (387 tuberculosis cases with a valid T-SPOT1.TB result and 304 with valid QFT-G-IT result), the NPV varied greatly, irrespective of the IGRA used.…”

Quantitative scoring of an interferon-γ assay for differentiating active from latent tuberculosis

“…However, the relevance of these results is debatable since, for the clinician, the challenge is not to distinguish between subjects who are naive to TB exposure versus active TB, but rather to distinguish active from latent disease among subjects who probably have been infected. Several studies have consistently shown higher production of IFN-c by lymphocytes challenged by M. tuberculosis-specific antigens in culture-proven active TB than in LTBI [16][17][18][19]. GOLETTI et al [19] compared the results of different IGRAs in patients with clinical suspicion of TB according to outcome (culture-proven TB versus alternative diagnosis established or resolution of clinical symptoms without drugs active against TB).…”

New tools and emerging technologies for the diagnosis of tuberculosis: Part I. Latent tuberculosis

“…In the absence of a gold standard for LTBI, active TB is used as a surrogate for LTBI. FIGURE 2 shows forest plots of sensitivity and specificity (for active disease) from studies that used the research or commercial versions of the QFT-G and T-SPOT.TB assays [23][24][25][26][27][28][29][30][31][32][33]. Overall, the plot shows high specificity (>95% in most studies).…”