Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_2758_Библиотеки_им_академика_М_И_Перельмана

Identication of the culprit medication causing a drug hypersensitivity reaction (DHR) is essential to prevent recurrence of an allergic reaction in the future. Prevention is the preferred approach to this clinical problem since cutaneous adverse drug reactions can be life-threatening or be com­plicated by signicant lifelong sequelae. However, identication of causal drug and recog­nition of possible drug cross-reactions can be challenging. In vitro assays are advantageous when compared to skin tests and provocation tests since there is no re-exposure to the suspect drug, making this form of allergy testing risk­free. Accurate diagnostic testing is necessary to avoid exclusion of tolerated medications and to identify medication that can be taken safely. The varied pathomechanisms underlying different DHR syndromes obliges the physician to select the most appropriate laboratory assay in order to minimise false negative results.

been reported to be high (93%) when serum tryptase is elevated, the negative predictive value (NPV) is low (17%) (Buka etal. 2017). Innate variation of blood levels necessitates careful exploration of optimal measurement timing. Modication of currently used tryptase threshold to a calculated ratio (1.2 × [basal tryptase level]+2μg/L) has been suggested (Baretto etal.

In Vitro Drug Allergy Testing

In the past serum drug-specic IgE (sIgE) was detected using the radioallergosorbent test (RAST), but this has now been superseded by enzyme linked immunosorbent assay (ELISA) or uoroenzyme immunoassay (FEIA) (Takazawa etal. 2019). Allergens bound to a carrier protein are embedded in a solid phase polymer. Serum from an affected patient is owed over the poly­mer chip. Allergen-specic IgE in the serum

allergen (drug)

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Y. X. Teo and M. R. Ardern-Jones

NMBA, chymopapain or tetanus toxoid does not necessarily equate to hypersensitivity and must be assessed in conjunction with the clinical his­tory (Demoly etal. 2014). Sensitivity and speci­city to β-lactam antibiotics varies between 0–85% and 52–100%, with reported values of 39–92% and 86–100% for NMDA (Decuyper etal. 2017). Similar to the acute phase reactants, the available time interval for sampling limits utility of testing to drug-specic IgE, as does the restricted spectrum and cost of commercially available assays. National Institute for Health and Care Excellence (NICE) review of diagnostic testing by specic IgE for immediate drug allergy reactions found that the quality of evidence was low and showed a high-false negative rate. This report concluded that blood testing for serum specic immunoglobulin E (IgE) to diagnose drug allergy should not be used in a non- specialist setting (Dworzynski et al. 2014; National Institute for Health and Care Excellence (NICE)

markers such as CD123 and human leukocyte antigen-DR (HLA-DR) are also labelled on analysed cells. Transition of intra- cellular ves­icles containing pre-formed mediators results in a pronounced rise of uorescence intensity on detection of surface CD63 with concomi­tant upregulation of CD203c (Fig.2). BAT has been validated in diagnosis of immediate drug hypersensitivity to NMBAs, beta-lactam anti­biotics, iodinated radiocontrast media, NSAIDs, chemotherapeutic agents and several biological agents. Despite this, there remains signicant variations in BAT test results (Campos et al. 2019; Mayorga et al. 2016). Direct assessment of basophils provides an advantage in assessment of non-IgE mediated pathways, including triggering of basophil degranulation by direct activation by opioids, iodinated contrast media, vancomycin and qui­nolones (McNeil etal. 2015). Studies differ on interpretation of positive ndings, although a twofold increase in stimulation index (calcu­lated by dividing mean uorescence intensity of stimulated compared to control cells) is gen­erally accepted (Campos etal. 2019). In gen­eral, the BAT has sensitivity between 40–90% and specicity of 80%, although this can be lower in testing to quinolones and NSAIDs. 6–17% of patients may not respond to stimula­tion (Hoffmann etal. 2015). In β-lactam antibi­otics, BAT performs better compared to drug-specic IgE although ndings may not corroborate with skin tests (De Week et al.

In Vitro Drug Allergy Testing

Transformation to blast cells (LTT)

IL-5, IL-13, IFN-γ)

Y. X. Teo and M. R. Ardern-Jones

2019) but the assay has been used with other

known delayed hypersensitivity drug culprits, such as anti-convulsants, NSAIDs, sulfanamides and quinolones.

In Vitro Drug Allergy Testing

ELISpot uses a similar approach, but the cells are exposed to drug directly on the anti-cytokine coated plate surface. Drug-specic T cells acti­vated on exposure to drug release cytokine into the area on the plate where the cells are adherent. Cytokine detection is undertaken in the same way with detection antibody and colorimetric ampli­cation. The localised cytokine release results in “spots”. Therefore the ELISpot test quanties the number of cells releasing a specic cytokine or other protein (e.g. IFN-γ, IL-4, IL-5, IL-17, granu­lysin, sFasL or granzyme B) following activation by the drug in question. The IFN-γ ELISpot has been the most widely used in drug hypersensitivity reactions, but other cytotoxic markers (granulysin and granzyme B) have also been assayed in severe cutaneous reactions (Porebski et al. 2011). Compared to the proliferation assays, these func­tional assays are advantageous as they are less reli­ant on cell proliferation, do not require use of radioisotopes, and can yield a result quickly.

Y. X. Teo and M. R. Ardern-Jones