title: Serodiagnosis of tuberculosis: specific detection of free and complex-dissociated antibodies anti-mycobacterium tuberculosis recombinant antigens.
abstract: The diagnostic test characteristics of detecting free and complex-dissociated IgG to three recombinant antigens of Mycobacterium tuberculosis (38-kDa, Ag16 and Ag85B), singly and in combination, were evaluated in sera from 161 tuberculous patients [smear-positive pulmonary TB (50), smear-negative pulmonary TB (pTBsm-) (60) and extrapulmonary TB (51)) and 214 control patients (mycobacteriosis (14), mycoses(14), leprosy(4), other underlying diseases (82) and healthy people (100)]. The individual antigens ranged from 25% to 42% in sensitivity and from 93% to 96% in specificity, while considering free IgG response. Addition of complex-dissociated antibodies against each individual antigen improved the sensitivity up to 55%. The number and levels of specific antibodies varied greatly from individual to individual. Combination of individual results for free and complex-dissociated IgG to 38-kDa, Ag16 and Ag85B offered 76% sensitivity and 83% specificity. When the three antigens were placed in the same well, the sensitivity was lower than that expected on the basis of single antigen (63%) but with a good specificity (95%), even in the group of mycobacteriosis or mycoses. The highest contribution of complex-dissociated IgG results to free IgG results was seen for the diagnosis of pTBsm- patients. In conclusion, although neither single recombinant antigen was reactive with most sera from TB patients even after the measurement of both free and complex-dissociated antibodies, the use of multi-antigen cocktails improved the diagnostic utility of the ELISA assay, allowing the identification of almost 70% of pTBsm-, with a high level of specificity; the use of additional, well selected antigens should lead to the detection of almost all patients with TB.
authors.affiliation: National Institute of Respiratory Diseases Emilio Coni, Santa Fe, Argentina. suimaz@yahoo.com
authors.forename: María Susana
authors.initials: MS
authors.lastname: Imaz
authors.forename: María Fernanda
authors.initials: MF
authors.lastname: Schmelling
authors.forename: Susanne
authors.initials: S
authors.lastname: Kaempfer
authors.forename: Ralph
authors.initials: R
authors.lastname: Spallek
authors.forename: Mahavir
authors.initials: M
authors.lastname: Singh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000907:Antibodies, Bacterial / Q000097:blood*; D000936:Antigen-Antibody Complex / Q000097:blood*; D000942:Antigens, Bacterial / Q000276:immunology*; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000175:diagnosis* / Q000276:immunology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000276:immunology; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D000936:Antigen-Antibody Complex; D000942:Antigens, Bacterial; D007074:Immunoglobulin G; D011994:Recombinant Proteins; C072681:Mycobacterium tuberculosis antigens