Mohammed Ahmed (Germany)
Ludwig-Maximilians University Division of Infectious Diseases and Tropical Medicine, University HospitalAuthor Of 1 Presentation
THE T-CELL ACTIVATION MARKER FOR TB (TAM-TB) IN “RAPAED-TB”- A NEW DIAGNOSTIC TOOL FOR PAEDIATRIC TB
Abstract
Backgrounds:
The diagnosis of tuberculosis (TB) in children remains the biggest hurdle in overcoming the epidemic. The blood-based T cell marker for TB assay (TAM TB) characterizes TB-specific CD4+ T cells based on the expression of surface markers. This approach allows a differentiation between latently and actively infected TB patients.
Methods
RaPaed-TB is a diagnostic validation study conducted in five countries enrolling children suspected of having TB. Alongside a thorough clinical and microbiological workup, a number of new tests are being evaluated including the TAM TB. The latter is a flow-cytometry based assay using a standardized kit which gives a result within 16-24h. Data cleaning is underway; presented data are preliminary and totals differ.
Results:
In total, 974 participants were enrolled with an overall microbiological confirmation rate (PCR/culture) of 24.2% (236/974), sufficient information for clinical case definition was available for 732 children. Overall, more than 890 TAM TBs were performed at enrolment. Using culture as reference standard, early analyses show a modest sensitivity of 60.8% (95%CI 48.8-72.0) and specificity of 83.5% (95%CI 77.0-88.9) in the overall cohort, with superior performance in children <1 year with a sensitivity of 80.0% (95%CI 51.9-95.7) and specificity of 85.0% (95%CI 62.1-96.8). Logistic regression was performed to explore determinants of TAM TB accuracy, generating strong evidence of TST-positivity increasing the odds for true-positivity in reference standard positive children by 5.06 (95%CI 1.83-13.99, p=0.0018). Further analyses are ongoing, and results are to be presented.
Conclusions/Learning Points:
RaPaed-TB is one of the largest TB diagnostic validation studies comparing several new tests ever performed in children. Presented data indicate a promising performance of TAM-TB, especially in the very young children.