7-2.b. Value of in vitro tests
The in vitro diagnostic method most frequently used for diagnosing
delayed HSRs is the lymphocyte transformation test (LTT). This test
identifies the proliferation of drug-specific T cells from patients with
HSR upon the stimulation with the suspected drug(s) by measuring the
incorporation of [3H].62 However, to our knowledge
there is only one study using this method with PPI. In this study LTT
was performed in 28 subjects with occupational allergy to omeprazole
diagnosed by positive patch test results. From these patients, 23 showed
a positive LTT result, yielding a sensitivity of 82%. From the 56
subjects with negative patch test results, 46 showed a negative LTT,
yielding a specificity of 82%.87 Another study has
analyzed the role of drug lymphocyte activation test (LAT) measuring
granulysin and interferon-γ in 69 cases of PPI delayed reactions
including SJS/TEN and DRESS.71 They found that LAT
measuring granulysin had a sensitivity of 59.3% and specificity of
96.4%.