Antituberculosis IgG antibodies as a marker of active Mycobacterium tuberculosis disease.
Anti-Mycobacterium tuberculosis IgG antibodies may aid in the diagnosis of active M. tuberculosis disease. We studied whether anti-M. tuberculosis IgG antibodies are elevated in active M. tuberculosis disease and assessed factors contributing to false-positive and -negative results. A retrospective study of 2,150 individuals tested by the QuantiFERON-TB Gold In-Tube (QFT-GIT) assay was conducted at the University of Utah, ARUP Laboratories, November 2008 to December 2010. All samples were tested with the InBios Active TbDetect antituberculosis (anti-TB) IgG antibody assay. Of 1,044 patients with a positive QFT-GIT, 59 (5.7%) were positive for M. tuberculosis antibodies. Fourteen of 1,106 (1.3%) with a negative or indeterminate QFT-GIT were positive for M. tuberculosis antibodies. M. tuberculosis antibody tests were positive in 61.5% with confirmed active M. tuberculosis disease and other mycobacterial infections. Over half of the false-negative M. tuberculosis antibody tests occurred in patients ≥ 90 years of age. False positives were seen in 12.9% of autoimmune patients. The odds ratio of being positive by the QFT-GIT and the InBios TB IgG assay increased with confirmed M. tuberculosis disease or highly suspected M. tuberculosis disease and was 86.7 (95% confidence interval [CI], 34.4 to 218.5) in these two groups compared to patients negative by both tests. Although anti-M. tuberculosis antibodies can be detected in patients with active M. tuberculosis disease, caution should be used with patients where immunoglobulin levels may be decreased or patients with autoantibodies.
University of Utah, ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, Utah, USA.
Ryan J
RJ
Welch
Kathleen M
KM
Lawless
Christine M
CM
Litwin
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D003951:Diagnostic Errors / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D011933:Reagent Kits, Diagnostic; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000175:diagnosis*; D014589:Utah; D055815:Young Adult
D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D011933:Reagent Kits, Diagnostic