Background . T-SPOT. TB is an interferon gamma release assay for detecting Mycobacterium tuberculosis infection. The requirement to process within 8 hours is constraining, deters use, and leads to invalid results. Addition of T Cell Xtend reagent may allow delayed processing, but has not been extensively field tested. Design . Consecutive AFB smear positive adult tuberculosis patients were prospectively recruited in Dar es Salaam, Tanzania. Patients provided a medical history, 1–3 sputum samples for culture and 1 blood sample which was transported to the laboratory under temperature-controlled conditions. After overnight storage, 25 μ L of T Cell Xtend reagent was added per mL of blood, and the sample was tested using T-SPOT. TB . Results . 143 patients were enrolled: 57 patients were excluded because temperature control was not maintained, 19 patients were excluded due to red blood cell contamination, and one did not provide a sputum sample for culture. Among 66 evaluable patients, overall agreement between T-SPOT. TB and culture was 95.4% (95%CI; 87.1–99.0%) with Kappa value 0.548. Sensitivity of T-SPOT. TB when using T Cell Xtend reagent was 96.8% (95%CI; 88.8–99.6%). Conclusions . When T Cell Xtend reagent is added to specimens held overnight at recommended temperatures, T-SPOT. TB is as sensitive as the standard assay in patients with tuberculosis.
Talbot, E. A., Maro, I., Ferguson, K., Adams, L. V., Mtei, L., Matee, M., & von Reyn, C. F. (2012). Maintenance of Sensitivity of the T-SPOT. TB Assay after Overnight Storage of Blood Samples, Dar es Salaam, Tanzania . Tuberculosis Research and Treatment, 2012, 1–4. https://doi.org/10.1155/2012/345290