Comparison of an in-house and a commercial RD1-based ELISPOT-IFN-gamma assay for the diagnosis of Mycobacterium tuberculosis infection.
OBJECTIVE
To compare a RD1-based in-house ELISPOT-interferon-gamma (IFN-gamma) assay with a commercial (T-SPOT.TB) assay for the diagnosis of Mycobacterium tuberculosis (TB) infection and the efficacy of the tuberculin skin test (TST) and ELISPOT assay in detecting latent TB infection (LTBI).


METHODS
Eighty-six subjects (65 household contacts of contagious TB-infected patients, 13 subjects with active or previous TB infection, and 8 with suspected TB infection) were consecutively recruited in the context of a surveillance program.


METHODS
Enrolled subjects underwent the Mantoux TST and two different ELISPOT-IFN-gamma assays: an in-house assay using a pool of selected M. tuberculosis peptides (MTP) and the commercial T-SPOT.TB assay.


RESULTS
The in-house and commercial ELISPOT-IFN-gamma assays showed almost complete concordance (99%) in diagnosing acute or LTBI. When comparing the efficacy of the TST with the in-house ELISPOT assay in detecting TB infection, a small agreement was observed (k=0.344, P<0.0001): 36% of the subjects with a positive TST were ELISPOT-MTP negative and 12% with a negative TST were ELISPOT-MTP positive. Furthermore, 78% of the ELISPOT-MTP negative individuals were ELISPOT- Bacillus Calmette-Guérin (BCG) positive, most of whom had received BCG vaccination.


CONCLUSIONS
Our in-house ELISPOT assay based on a restricted pool of highly selected peptides is equivalent to the commercial T-SPOT.TB assay, is cheaper and is probably not confounded, unlike the TST, by BCG vaccination in our setting.
Mantegani
Paola
P
Clinic of Infectious Diseases, San Raffaele Scientific Institute, Via Stamira D'Ancona 20, 20127, Milano, Italy.
Piana
Federica
F
Codecasa
Luigi
L
Galli
Laura
L
Scarpellini
Paolo
P
Lazzarin
Adriano
A
Cirillo
Daniela
D
Fortis
Claudio
C
D000293:Adolescent; D000328:Adult; D000368:Aged; D001426:Bacterial Proteins / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques / Q000592:standards; D007223:Infant; D007371:Interferon-gamma / Q000276:immunology*; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D010455:Peptides / Q000276:immunology*; D011933:Reagent Kits, Diagnostic / Q000592:standards; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000175:diagnosis / Q000276:immunology*
D001426:Bacterial Proteins; D010455:Peptides; D011933:Reagent Kits, Diagnostic; D007371:Interferon-gamma