Predictors for false-negative QuantiFERON-TB Gold assay results in patients with extrapulmonary tuberculosis

Extrapulmonary tuberculosis (EPTB) is a heterogeneous disease, and diagnosis is sometimes difficult. We investigated the diagnostic performance of the QuantiFERON-TB Gold assay (QFT-GIT) according to sites of EPTB and predictors for false-negative QFT-GIT results.

A total of 2176 patients were registered with active TB from January 2012 to December 2016 in Seoul St. Mary's Hospital, a 1200-bed tertiary teaching hospital in Seoul, Korea. We retrospectively reviewed the medical records of 163 EPTB patients who underwent QFT-GIT.

False negative QFT-GIT results were found in 28.8% (95% CI 0.22-0.36) of patients with EPTB. In the proven TB group, negative QFT-GIT results were found in 28.6% (95% CI 0.04-0.71) of pleural, 8.3% 0.002-0.38of lymph node, 8.3% (95% CI 0.002-0.38) of skeletal and 5.8% (95% CI 0.001-0.28) of gastrointestinal TB cases. Among probable TB cases, QFT-GIT negative results were identified in 46.2% (95% CI 0.19-0.75) of skeletal, 33.3% (95% CI 10-0.65) of pericardial, 30.8% (95% CI 0.09-0.61) of pleural and 17.2% (95% CI 0.10-0.56) of gastrointestinal TB cases. In the possible TB cases, central nervous system TB (n = 21) was most frequent, and 66.7% (95% CI 0.43-0.85) of those showed QFT-GIT negative results. By multivariate analysis, possible TB was independently associated with false-negative QFT-GIT results (OR 4.92, 95% CI 1.51-16.06, p = 0.008).

Prudent interpretation of QFT-GIT results might be needed according to anatomic site of involvement and diagnostic criteria in patients with high suspicion of EPTB.