Clinical Usefulness of Combined Anti-tuberculosis Antibody Test and Interferon-gamma Release Assay for the Diagnosis of Tuberculosis

ABSTRACT

BACKGROUND: For the diagnosis of tuberculosis (TB), a variety of tests based on the patients' immune response has been introduced. We evaluated the clinical usefulness of combined anti-tuberculosis antibody (anti-TB Ab) test and Interferon-gamma release assay (IGRA), evaluating humoral and cellular immune response to Mycobacterium tuberculosis, respectively. METHODS: Among patients tested for IGRA, 78 patients diagnosed as TB and treated with anti-TB drug and 80 non-TB patients were included in this study. We used QuantiFERON-TB GOLD (QFT, Cellestis limited, Australia) for IGRA and an immunochromatographic assay, Easy Test TB (ASAN PHARM, Korea), for anti-TB Ab test. RESULTS: The sensitivity, specificity, and positive and negative predictive values of Easy Test TB were 23.1%, 98.8%, 94.7% and 56.8%, respectively. QFT had a significantly higher sensitivity than Easy Test TB (67.9% vs. 23.1%; P<0.05). The agreement between the two assays was poor (69.6%, k=0.190). Of the 18 cases with positive Easy Test TB, six (33%) showed negative QFT results. The combination of Easy Test TB and QFT had a significantly higher sensitivity than single QFT (75.6%, vs. 67.9%; P=0.031). CONCLUSIONS: The combination of Easy Test TB and QFT could be used to aid in a rapid diagnosis and early treatment of TB.