Accuracy of an immune diagnostic assay based on RD1 selected epitopes for active tuberculosis in a clinical setting: a pilot study

Abstract

A previous case-control study reported that an in-vitro interferon (IFN)-gamma response to early secreted antigenic target (ESAT)-6 selected peptides was associated with active tuberculosis (A-TB). The objective of the present pilot study was to evaluate the diagnostic accuracy of this assay for TB disease in a clinical setting. An IFN-gamma ELISPOT assay was performed on samples from patients with suspected A-TB using two peptides selected from ESAT-6 protein and three peptides selected from culture filtrate 10 (CFP-10) proteins. The results were compared with those obtained by two commercially available assays approved for diagnosis of TB infection (T SPOT-TB and QuantiFERON-TB Gold) which use ESAT-6/CFP-10 (RD1) overlapping peptides. Sensitivity to the RD1 selected peptides was 70% (positive for 16 of 23 patients with microbiologically diagnosed A-TB) and specificity was 91% (positive for three of 32 controls). In contrast, the sensitivity and specificity were 91% and 59%, respectively, for T SPOT-TB, and were 83% and 59%, respectively, for QuantiFERON-TB Gold. The RD1 selected peptides assay had the highest diagnostic odds ratio for A-TB. Thus, the results suggest that an assay based on RD1 selected peptides has a higher diagnostic accuracy for A-TB in a clinical setting compared with commercially available assays based on RD1 overlapping peptides.

Effect of HIV-1 Infection on T-Cell–based and Skin Test Detection of Tuberculosis Infection

“…Preliminary doubt that these assays can be applied to HIV-infected people has been raised (16,17) although ELISpot-based analyses report encouraging sensitivity (73-90%) for active HIV-associated tuberculosis in both children and adults (18,19). There have been relatively few published three-way comparisons of these tests (20)(21)(22), and no study has systematically assessed the decrement in sensitivity that might be conferred by HIV infection in comparable HIVinfected and uninfected persons. Further, studies in developing country environments are few.…”

Response to Rv2628 latency antigen associates with cured tuberculosis and remote infection

“…There is evidence that commercial IGRAs are highly sensitive for detecting LTBI [2], and have a high specificity that is unaffected by bacille Calmette-Guérin (BCG) vaccination. Although IGRAs were designed as assays for LTBI, these tests do not discriminate between active disease and LTBI [5,6]. Moreover, IGRAs do not distinguish between a recently acquired infection and remote LTBI [7].…”

The specificity of interferon- -based blood tests in the identification of latent tuberculosis infection

“…First, LEE et al [2] demonstrated that T-SPOT.TB has higher sensitivity than QuantiFERON-TB Gold in the diagnosis of culture-confirmed active TB disease, and this finding has also been reported by GOLETTI et al [3]. Whilst active TB disease is clearly not the same as LTBI, it might be hypothesised that this difference in sensitivity is also true in LTBI.…”