Sensitivity and specificity of the lymphocyte transformation test in drug reaction with eosinophilia and systemic symptoms causality assessment.

BACKGROUND: Drug reaction with eosinophilia and systemic symptoms (DRESS) is a severe delayed hypersensitivity reaction. The determination of drug causality is complex. The lymphocyte transformation test (LTT) has been reported positive in more than 50% of DRESS cases. Nevertheless, the sensitivity and specificity of LTT specifically in DRESS have not yet been established. Rechallenge with the culprit drug is contraindicated and cannot be used as gold standard for sensitivity and specificity determination. OBJECTIVE: To estimate the sensitivity and specificity of LTT in a clinically defined series of patients with DRESS. METHODS: Some 41 patients diagnosed with DRESS were included in the study. The results of the algorithm of the Spanish Pharmacovigilance System were used as the standard for a correct diagnosis of drug causality. A standard LTT was performed with involved drugs in acute or recovery samples. A stimulation index (SI) ≥2 in at least one concentration except for beta-lactams (SI ≥3) and contrast media (SI ≥4) was considered positive. Contingency tables and ROC curves were used for analysis. RESULTS: Sensitivity and specificity of LTT in the recovery phase of DRESS were 73% and 82%, respectively, whereas in the acute phase, they were only 40% and 30%, respectively. Comparison of skin tests and LTT confirmed a higher sensitivity and specificity of LTT in DRESS. LTT showed high sensitivity (S) and specificity (Sp) for anticonvulsants (S 100%, Sp 100%; P = .008), anti-TB drugs (S 87.5%, Sp 100%; P = .004), and beta-lactams (S 73%, Sp 100%; P = .001). ROC curves revealed that the best criteria for LTT positivity for all drugs are SI ≥2 in at least one concentration, increasing overall sensitivity to 80%, and for beta-lactams from 73% to 92%. CONCLUSIONS AND CLINICAL RELEVANCE: LTT is a good diagnostic tool for drug causality in DRESS, mainly when performed in the recovery phase.

A novel multiplex polymerase chain reaction assay for detection of both HLA-A*31:01/HLA-B*15:02 alleles, which confer susceptibility to carbamazepine-induced severe cutaneous adverse reactions.

HLA-A*31:01 and HLA-B*15:02 have been widely reported to confer genetic susceptibility to carbamazepine (CBZ)-induced severe cutaneous adverse reactions (SCARs). Accordingly, the screening for these alleles has been highly recommended to prevent SCAR prior to introducing CBZ therapy. Although a number of methods are available for screening of HLA-A*31:01 or HLA-B*15:02 alleles separately, developing an assay that can detect both these alleles would be more clinically practical, cost-effective and less time-consuming. Therefore, in this study, a multiplex polymerase chain reaction (PCR) using TaqMan Probe was designed and validated to be able to detect HLA-A*31:01 and HLA-B*15:02. In comparison with Luminex-SSO/SBT/SSB, the multiplex PCR assay for detection of HLA-A*31:01 and HLA-B*15:02 had a perfect agreement in the validation group of 125 samples. The method was able to detect the target genes at the DNA concentration of 0.037 ng/µL. The unit cost of this assay is less than $5 USD with total time of 110 minutes.

Clinical application of pharmacogenomics: the example of HLA-based drug-induced toxicity.

Pharmacogenomics is gradually becoming more and more indispensable in modern medicine. In several cases, a pharmacogenomics test may alleviate serious drug-induced adverse reactions, if it precedes drug prescription. In this article, we provide an overview of the well-established HLA-based carbamazepine- and allopurinol-induced adverse reactions, as one of the most characteristic examples of the clinical application of pharmacogenomics, highlighting its regional impact in Southeast Asian populations in preventing adverse reactions of certain drug/allele pairs. This example provides useful insights towards evidence generation for policy implementation, including economic evaluation analysis, the implementation of pharmacogenomics testing procedures and monitoring of policy effectiveness, hence serving, per se or in the context of international collaborative efforts, as a model for similar cases in several national healthcare systems worldwide.

HLA-B*5801: utility and cost-effectiveness in the Asia-Pacific Region.

Gout is a common condition which is mainly treated with the hypo-uricemic agent, allopurinol. Although allopurinol is generally a well-tolerated drug, there is a small risk of developing potentially fatal complications, such as allopurinol hypersensitivity syndrome. Recent advances in pharmacogenomics have made possible the identification of genes which confer susceptibility to specific drugs. A recent multi-national case-control study has reported allopurinol as the most common drug associated with Stevens-Johnson syndrome and toxic epidermal necrolysis. Several studies have established a strong association between the human leukocyte antigen (HLA)-B*5801 gene and development of Stevens-Johnson syndrome and toxic epidermal necrolysis. The allele frequency of HLA-B*5801 is highest in the South East Asian population.Since other hypo-uricemic agents are available, patients may wish to have HLA-B*5801 testing before being started on allopurinol. As the test for HLA-B*5801 is expensive, time-consuming and only available in selected laboratories, there is a need to evaluate the utility and cost-effectiveness of this test in our region.