Use of the T-SPOT.TB assay to detect latent tuberculosis infection among rheumatic disease patients on immunosuppressive therapy.
OBJECTIVE
We evaluated the T-SPOT.TB assay to identify latent tuberculosis infection (LTBI) in patients with rheumatic disease receiving immunosuppressive medication including tumor necrosis factor (TNF) antagonists.


METHODS
A total of 200 patients seen in the Arthritis Center at Brigham and Women's Hospital were enrolled for study. Most patients were US-born women with rheumatoid arthritis. A medical history was obtained using a questionnaire, whole blood was drawn for the T-SPOT.TB assay, and tuberculin skin testing (TST) was performed.


RESULTS
Both tests were performed on 179 subjects, who had no history of a positive TST. All subjects had a strong response to the T-SPOT.TB test positive control, and there were no indeterminate results. Among these 179 subjects, 2 had a positive TST and 10 had a positive T-SPOT.TB test. No subject was positive for both tests. Patients with a positive T-SPOT.TB test did not have typical risk factors for LTBI based on clinical evaluation.


CONCLUSIONS
The lack of concordance between the TST and the T-SPOT.TB assay may indicate that the immunoassay is more sensitive, particularly in a patient population taking immunosuppressive medications. It is equally likely that the low prevalence of LTBI in this low-risk population led to an increase in the false-positive rate despite the high sensitivity and specificity of the T-SPOT.TB assay. In the context of our patient population, the T-SPOT.TB assay is likely to be most useful in evaluation of patients with a positive TST, since these patients have a higher pretest probability of having LTBI.
Behar
Samuel M
SM
Brigham and Women's Hospital, Boston, MA 02492, USA. sbehar@rics.bwh.harvard.edu
Shin
Daniel S
DS
Maier
Agnes
A
Coblyn
Jonathan
J
Helfgott
Simon
S
Weinblatt
Michael E
ME
D000328:Adult; D000368:Aged; D018501:Antirheumatic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007118:Immunoassay; D016867:Immunocompromised Host; D007166:Immunosuppressive Agents / Q000009:adverse effects / Q000627:therapeutic use*; D007371:Interferon-gamma / Q000032:analysis; D008297:Male; D008875:Middle Aged; D011933:Reagent Kits, Diagnostic; D012216:Rheumatic Diseases / Q000150:complications / Q000188:drug therapy / Q000276:immunology*; D014376:Tuberculosis / Q000175:diagnosis* / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors*
D018501:Antirheumatic Agents; D007166:Immunosuppressive Agents; D011933:Reagent Kits, Diagnostic; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma