Comparing Consistency of QuantiFERON-TB Gold Plus and QuantiFERON-TB Gold for Latent Tuberculosis in Dialysis Population

Tuberculosis (TB) remains one of the most important infectious diseases worldwide. According to the World Health Organization (WHO) estimates, there were 9 million new TB cases and 1.5 million related deaths in 2013. Future control strategies include early treatment for preventing transmission and treatment of latent TB infection (LTBI) for reducing reactivation. Patients with renal failure undergoing dialysis have increased risk of TB due to attenuated cellular immunity. For instance, their risk of developing active TB in the dialysis population is 7.8-25 times higher than that of the general population. However, TB diagnosis is usually delayed because of frequent extra-pulmonary manifestations. Thus, LTBI detection in this specific group is important.

Positive results of interferon-gamma release assays (IGRAs) and the exclusion of active TB are the current diagnostic bases of LTBI, which is a precursor of tuberculosis reactivation. However, recent reports show a high negative reversion rate of quantiFERON Gold In-tube (QFT-GIT), a kind of IGRA, in cohorts of health care workers (33% after 18 weeks) close TB contacts (35% after six months), and patients receiving long-term dialysis (46% after six months). This phenomenon questions the clinical significance of a single positive IGRA result. Increasing the IGRA threshold or doing serial follow-up to improve specificity have both been suggested but there is no comparison by the risk of TB development.

Therefore, increasing the accuracy and stability and then improving the rate of negative conversion from positive IGRA results are very important. Currently, new generation of QuantiFERON-TB Gold Plus includes two tubes for CD4 and CD8 T cells response, which can indicate TB immune response more specifically. The investigators applied this project to compare the performance of diagnosing LTBI by QuantiFERON-TB Gold Plus in comparing QuantiFERON-TB Gold In-tube.