title: Detecting latent tuberculosis infection during anti-tumor necrosis factor therapy.
abstract: OBJECTIVE
  There is little information regarding the reliability of repeat tuberculin skin tests (TSTs) and interferon gamma release assays (IGRAs) in detecting latent tuberculosis infection (LTBI) in people on anti-tumour necrosis factor (TNF) medication.
  
  
  METHODS
  We conducted a prospective, observational study of patients referred to the Saskatoon Tuberculosis (TB) Clinic prior to starting anti-TNF medication. A chest x-ray (CXR), 2-step TST and IGRA (QuantiFERON-TB Gold In-Tube Method) were performed at baseline. Those patients with a baseline TST ≥10 mm and/or a positive IGRA were followed with a clinic visit, CXR, TST and IGRA at 3 and 6 months after starting anti-TNF medication.
  
  
  RESULTS
  Of 106 potential patients, 91 consented to participate. Twenty-six patients had a positive (≥ 10 mm) TST or IGRA at baseline; twelve started and stayed on anti-TNF medication through the 6-month follow-up and completed both planned follow-up visits. The baseline mean TST measurement for the 12 participants was 13.9 mm (SD 11.4), increasing to a mean of 16.8 mm (SD 9.3) post-booster. At 3 months post-anti-TNF initiation, there was an overall decrease in TST measurement (mean=10.0 mm; SD 9.3; p=0.013), with measurements <5 mm in 3 of the 12 patients. By the 6-month TST, a response recovery was observed with a mean TST measurement of 14.5 mm (SD 7.7), with 11/12 ≥5 mm. The IGRA was unchanged throughout the study period in all patients. The overall agreement between TST and IGRA was poor (kappa coefficient = 0.180, p=0.020).
  
  
  CONCLUSIONS
  We demonstrated a transient but significant decrease in TST response in the first six months of anti-TNF therapy.
authors.affiliation: Department of Medicine, Division of General Internal Medicine, University of Alberta, Edmonton, Canada. jennifer.ringrose@ualberta.ca
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Ringrose
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Sanche
authors.forename: Regina M
authors.initials: RM
authors.lastname: Taylor-Gjevre
mesh_terms: D000068879:Adalimumab; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized / Q000627:therapeutic use; D018501:Antirheumatic Agents / Q000627:therapeutic use; D000068800:Etanercept; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000627:therapeutic use*; D000069285:Infliximab; D055985:Latent Tuberculosis / Q000150:complications / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013902:Radiography, Thoracic / Q000592:standards*; D018124:Receptors, Tumor Necrosis Factor / Q000627:therapeutic use*; D015203:Reproducibility of Results; D012216:Rheumatic Diseases / Q000150:complications / Q000188:drug therapy*; D014374:Tuberculin Test / Q000592:standards*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D018501:Antirheumatic Agents; D007074:Immunoglobulin G; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab; D000068879:Adalimumab; D000068800:Etanercept