Table 3.

Role of diagnostic/screening tests in immediate and delayed drug hypersensitivity reactions.

	In Vivo				Ex Vivo
Phenotype	SPT/IDT	Patch test	Oral Challenge (DPT)	LTT	ELISpot ICS/other ex vivo	BAT	IgE/RAST	HLA Screen
IgE mediated	Yes	No	Yes	No	No	Not routine (specific not sensitive)	Yes-screen only (specific not sensitive)	No
Delayed Rash (MPE)	Yes -delayed IDT reading	Yes	Possible 5–7 day challenge	Yes	Yes	No	No	No
DRESS/DIHS	Yes - delayed IDT reading	Yes	No	Yes	Yes	No	No	Possible†
Abacavir HSS	No -risk severe reaction	Yes	No	Yes	Yes	No	No	Yes HLA-B*5701
SJS/TEN	Low sensitivity	Low sensitivity	No	Yes	Yes	No	No	Possible†
AGEP	Yes -delayed IDT reading	Yes	No	Possible‡	Possible	No	No	No
FDE	Yes- delayed IDT reading	Yes	No	Possible‡	Limited data	No	No	No
DILI	No	No	No	Possible	Yes	No	No	Possible†

^†Not routinely used globally in clinical practice as positive predictive value, negative predictive value and number needed to test to prevent one case varies amongst drugs and populations (see Table 4).

^‡Limited data on the performance of LTT on AGEP and FDE. However along with a positive delayed IDT and patch test result as well as a good clinical diagnosis, a positive LTT can help in the identification of the culprit drug. ¹³⁹ Yet diagnosis should take into account the possibility false positive and negative results, particularly in cases where multiply drugs are under suspicion.

HLA: human leukocyte antigen, LTT: Lymphocyte transformation test, ELISpot: enzyme-linked immunospot, ICS: intracellular cytokine staining, BAT: Basophil Activation Testing, Ig: Immunoglobulin, IDT: intradermal testing, SPT: skin prick testing, HSS: Hypersensitivity syndrome, DRESS: Drug reaction with eosinophilia and systemic symptoms, DIHS: Drug-induced Hypersensitivity syndrome, SJS/TEN: Stevens-Johnson syndrome / Toxic epidermal necrolysis, AGEP: acute generalised exanthematous pustulosis, DILI: Drug-induced liver injury, FDE: Fixed drug eruption.