Weir C, Li J, Fulton R, Fernando SL. Development and initial validation of a modified lymphocyte transformation test (LTT) assay in patients with DRESS and AGEP.
ALLERGY, ASTHMA & CLINICAL IMMUNOLOGY 2022;
18:90. [PMID:
36210462 PMCID:
PMC9548132 DOI:
10.1186/s13223-022-00729-4]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 09/24/2022] [Indexed: 11/17/2022]
Abstract
Background
The lymphocyte transformation test (LTT) is an in vitro assay used to diagnose drug induced hypersensitivity reactions by detecting the activation and expansion of drug-specific memory T cells to the suspected implicated drug. Traditionally radiolabelled thymidine (3H-thymidine) has been used but requires the handling and disposal of radioactive materials.
Objective
To examine safe alternatives to 3H-thymidine, test assay modifications for improved assay sensitivity and evaluate the modified LTT in patients with DRESS and AGEP.
Methods
Four proliferation detection assays (BRDU, CyQUANT™, MTT and XTT) were screened for LTT sensitivity. XTT the most sensitive and practical was selected for further evaluation Modifications like autologous serum (AS) and regulatory T cell depletion (T-REG) were tested for improved assay sensitivity. Finally, an initial evaluation of the XTT–LTT was performed in 8 patients with DRESS and 2 with AGEP including cytokine testing.
Results
Of the non-radioactive alternatives we tested, XTT a colorimetric assay was the most sensitive and practical to move to evaluation. The addition of AS increased background signal. Depletion of T-REGs improved sensitivity but cell sorting time and risk of contamination limited benefit.
Of eight patients diagnosed with DRESS and 2 with AGEP tested with XTT–LTT assay results showed our assay matched clinical findings of implicated drugs in 8/10 patients when using a stimulation index (SI) ≥ 2 and 8/10 with analysis by ANOVA. All ten patients were correctly diagnosed by either analysis.
Conclusion
XTT appears to be a safe, viable alternative to 3H-thymidine, with high sensitivity and allowing direct cytokine quantification on specific patient cells.
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