Novel Reliable Assay for Tuberculosis and LTBI Tested

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB) complex organisms, is still one of the most prevalent human infections worldwide estimated in 2018 with 1.2 million deaths among human immunodeficiency virus (HIV)-negative people and an additional 251,000 deaths from TB among HIV-positive people.

Additionally, 1.7 billion people in the world’s population harbor a latent tuberculosis infection (LTBI) and thus they are at risk of developing active TB disease during their lifetime Consequently, urgent action is required to improve the diagnosis of both active TB and latent infection in order to set-up new screening tests for MTB that can be used for public health to detect and treat individuals who are at high risk of developing active TB.

Clinical scientists at the University of Florence (Florence; Italy) and their colleagues consecutively enrolled a total of 250 subjects that included 151 healthy subjects, 66 active TB patients and 33 subjects with LTBI. Diagnosis of active TB cases relied on clinical, microbiological and radiological findings. A group of 139 blood donors was recruited in Blood Center, Almaty, Kazakhstan; they were designated as “conditionally healthy” since all were negative by annual fluorographic examination.

The blood of all the patients was tested with LIOFeron TB/LTBI assay (Lionex GmbH (Braunschweig, Germany), containing MTB alanine dehydrogenase, able to differentiate active TB from LTBI diagnosis. This assay is an interferon-gamma release assay (IGRA) and the optical density (OD) was quantified at 450 nm with a spectrophotometer (Multiskan Go, Thermo Scientific, Waltham, MA, USA). For comparison the assay was compared with the QuantiFERON-TB Gold Plus assay (Qiagen, Hilden, Germany).

The investigators reported that the two assays demonstrated an excellent concordance of their results with patients’ diagnosis of MTB infection. Receiving Operating Characteristic (ROC) analysis for QuantiFERON-TB Gold Plus showed sensitivity and specificity respectively of 98% and 97% in diagnosing active TB patients and 85% and 94% in diagnosing LTBI subjects. LIOFeron TB/LTBI assay showed sensitivity and specificity respectively of 90% and 98% in diagnosing active TB patients and 94% and 97% in diagnosing LTBI subjects.

The authors concluded that the LIOFeron TB/LTBI assay displayed the same high accuracy as the QuantiFERON-TB Gold Plus test in diagnosing MTB infection/TB disease, and demonstrated higher sensitivity than QuantiFERON-TB Gold Plus test in LTBI detection. The study was published in the February, 2020 issue of the International Journal of Infectious Diseases.

Related Links:
University of Florence
Lionex GmbH
Thermo Scientific
Qiagen