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Objective Patients who develop interferon-gamma autoantibodies (IFN-ɤ autoAbs) in adult-onset immunodeficiency (AOID) syndrome are more likely to develop opportunistic and recurrent intracellular infections. The assay to detect IFN-ɤ autoAbs is essential for the diagnosis and therapeutic monitoring of AOID syndrome. Therefore, this study applied the QuantiFERON assay for the detection of IFN-ɤ autoAbs. Methods Serum from patients with AOID syndrome (n = 19) and serum from healthy patients (n = 20) was collected and applied using 2 neutralizing platforms of enzyme-linked immunosorbent assay (ELISA) kits (the BD ELISA and the QuantiFERON ELISA) for IFN-ɤ autoAbs detection. Results The pooled serum from patients with AOID syndrome showed >50% inhibition at 1:5000 dilution (positive), whereas the pooled serum from healthy patients showed <50% inhibition at 1:5000 dilution (negative) according to the neutralizing QuantiFERON ELISA. Each specimen showed the same result according to both the neutralizing BD ELISA and the neutralizing QuantiFERON ELISA. Moreover, the patient serum showed a variation in titer ranging from 1:5000 to >1:5,000,000 according to the neutralizing QuantiFERON ELISA. Conclusion The QuantiFERON ELISA kit could be applied for the detection of IFN-ɤ autoAbs for the diagnosis and therapeutic monitoring of AOID syndrome. [ABSTRACT FROM AUTHOR]