Role of Quantiferon gold assay in the detection and follow-up of treatment of latent tuberculosis infection in some acquired immune-compromised patients

Abstract

Background In patients latently infected with Mycobacterium tuberculosis, immunosuppression increases the risk of progression to active tuberculosis (TB), which is still considered one of the difficult and frequent opportunistic infections worldwide. Better specificity in the diagnosis of latent tuberculosis infection (LTBI) is shown by Quantiferon-TB Gold In-Tube (QFT-GIT), and has been accepted in many national TB programs in low-endemic countries; QFT-GIT relies on detection of the immune reaction to specific M. tuberculosis antigens, which are not found in Bacillus Calmette–Guérin (BCG) or certain non-TB mycobacteria. Aim The aim of this study is to determine the role of the QFT-GIT assay in the detection and follow-up of treatment of latent tuberculosis (LTB) in some acquired immune-compromised patients. Participants and methods This prospective study was carried out on 50 immune-compromised patients attending the Abbassia Chest Hospital (either as inpatients or as outpatients). All patients were subjected to an assessment of history and clinical examination, radiological work-up, and laboratory investigations. All patients enrolled in the study were sputum negative for acid-fast Bacilli by Ziehl–Neelsen stain. Both the tuberculin skin test (TST) using the Mantoux technique and the QFT-GIT assay were performed simultaneously and their results were statistically compared, and then QFT-GIT was repeated after preventive treatment. Results The sensitivity of QFT-GIT was 20.8% and the sensitivity of TST was 12.5%. The frequency of LTB according to TST was only two (4.5%), that of the QFT-GIT test was only six (12.5%), and that of both QFT-GIT and TST was four (8.3%). Positive QFT-GIT was greater in patients receiving steroids, whereas indeterminate results were found only among HIV patients. Also, positive TST was greater among patients receiving steroids. There was a statistically significant difference between the CD4 count and the results of Quantiferon in HIV patients; indeterminate results were found in patients with CD4 less than 200 cells/mm3. There was a statistically significant reduction in quantitative QFT-GIT in LTB patients after preventive treatment. Conclusion The QFT-GIT assay seems to be more sensitive for the detection of LTBI in immune-compromised patients compared with the TST; however, QFT-GIT gave a considerable proportion of indeterminate results among HIV infected patients. Therefore, the simultaneous use of both TST and QFT-GIT could maximize the screening efficacy for LTBI in immune-compromised patients. The quantitative QFT-GIT assay can be used to monitor the effect of preventive treatment.

Keywords

• immune-compromised
• latent tuberculosis infection
• quantiferon-tb gold-in-tube