Contradictory Results between T-SPOT.TB and QFT-3G in Patients with Respiratory Symptoms

A 60-year-old male who presented with cough and fever (case 1), and a 77-year-old female with hemoptysis (case 2) were admitted to IUHW Shioya Hospital. Interferon gamma release assay (IGRA: QFT-3G and T-SPOT.TB) were both performed on each patient; the QFT-3G was positive and T-SPOT.TB was negative in both cases despite different final diagnosis. While case 1 was determined to have active tuberculosis, in case 2 active tuberculosis was eliminated as the diagnosis. The contradictory results in these patients should serve as a reminder to clinicians that they should not rely on the results of IGRA testing for the diagnosis of active tuberculosis.