Background. Cutaneous drug reactions are common but diagnostically challenging due to phenotypic heterogeneity and\r\nsimultaneous exposure to multiple drugs. These limitations prompted the development of diagnostic tests. Aims. To evaluate the\r\nperformance of an in vitro assaymeasuring interferon-gamma release from patients� lymphocytes in the presence of causative drugs\r\nfor the diagnosis of drug reactions. Methods. Mononuclear cells derived from patients were incubated with and without suspected\r\ndrugs, and increment of interferon-gamma levels was measured by ELISA.We performed a telephonic survey to evaluate the effect\r\nof stopping the drugs incriminated by the assay on cutaneous manifestations. Results. We assessed 272 patients who used 1035\r\nmedications.When assessed against the questionnaire data collected at least 6 months after stopping the causative drug, sensitivity\r\nwas found to be 83.61% and specificity 92.67%. Likelihood ratio for a positive test is 11.40 and for a negative test 0.18. Positive\r\npredictive value is 75.37% and negative predictive value is 95.47%. The test was found to performsignificantly better in females and\r\nin older patients. Conclusions. Interferon-gamma release test is a useful adjunct tool in the diagnosis of cutaneous drug reactions.
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