Impact of Processing Delays and Cryopreservation on Sensitivity and Specificity of the Lymphocyte Transformation Test

In the lymphocyte transformation test (LTT), peripheral blood mononuclear cells (PBMCs) from patients with presumed drug allergy are cultured with the implicated drug. No study has systematically investigated how delayed processing or cryopreservation of PBMCs affects the sensitivity and specificity of the LTT to detect a drug sensitization. We evaluated the impact of delayed processing or cryopreservation of PBMCs on the sensitivity and specificity of the LTT focusing on interferon-y (IFN-γ) secretion as read-out. Additionally, we investigated the impact of the respective processing methods on non-stimulated reference and TT-stimulated PBMCs.

Blood from 30 patients and 30 gender-matched controls was split for paired processing: one aliquot was processed immediately as internal reference of the patient/control, the other subjected to either a 24-h delay (n = 15) or immediate processing followed by cryopreservation of the PBMCs (n = 15). Thereby, each patient and control in the respective cohort served as its own reference for the assessment of the methodical processing impact. IFN-γ concentrations in PBMC culture supernatants were measured by ELISA.

Cryopreservation of PBMCs resulted in a statistically non-significant trend toward higher sensitivity (45% vs. 32%) and specificity (81% vs. 79%), for detecting drug sensitization compared to delayed processing. Overall, 80% of the LTT results using cryopreserved PBMCs were consistent with those obtained from the immediately processed reference group.

Due to the lack of statistical significance, no clear recommendation for one of the two processing methods can be made.