Flow-assisted allergy diagnosis: current applications and future perspectives

Physicians predominantly rely upon quantification of serum-specific immunoglobulin E (IgE) and/or skin test to confirm clinically suspected IgE-mediated allergy. However, for various reasons, identification of the offending allergen(s) and potentially cross-reactive structures is not always straightforward. Flow-assisted allergy diagnosis relies upon quantification of alterations in the expression of particular basophilic activation markers. Actually, upon challenge with a specific allergen, basophils not only secrete quantifiable bioactive mediators but also upregulate the expression of different markers which can be detected efficiently by flow cytometry using specific monoclonal antibodies. Currently, the technique has been applied in the investigation of IgE-mediated allergy caused by classical inhalant allergens, food, Hevea latex, hymenoptera venoms and drugs. It is also appreciated; the technique proves valuable in the diagnosis of non-IgE-mediated (anaphylactoid) reactions such drug hypersensitivity and the detection of autoantibodies in certain forms of chronic urticaria. This review will not address immunologic features, characteristics and general pitfalls of flow-assisted analysis of in vitro-activated basophils as summarized elsewhere. After a recapitulation of the principles and some specific technical issues of flow-assisted analysis of in vitro-activated basophils, we principally focus on the current clinical and research applications of the basophil activation tests. Personal experience of both research groups is provided, where appropriate. Finally, a viewpoint on how the field might evolve in the following years is provided.

Flow-assisted diagnostic management of anaphylaxis from rocuronium bromide

BACKGROUND

Diagnosis of anaphylaxis from neuromuscular blocking agents (NMBA) is not always straightforward.

OBJECTIVES

To assess flow cytometric analysis of activated basophils (BAT) as a diagnostic instrument in anaphylaxis from rocuronium. To investigate whether the technique might help to identify cross-reactive and safe alternative compounds.

METHODS

For validation of the BAT, 14 patients with perioperative anaphylaxis demonstrating a positive skin test (ST) for rocuronium and eight individuals that tolerated rocuronium and a negative ST for this drug were enrolled. To confirm specificity of the BAT, five patients that tolerated atracurium or cisatracurium with a negative ST for rocuronium were tested. Basophil activation with rocuronium, vecuronium, atracurium, cisatracurium and suxamethonium was analysed flow cytometrically by labelling with anti-CD123/anti-HLADR/anti-CD63.

RESULTS

Sensitivity of BAT for rocuronium was 91.7% and specificity 100%. However, in two patients the BAT was lost as a diagnostic tool, as their cells were nonresponsive to positive control stimulation and allergen. Seven from the 12 responsive patients also demonstrated a clear basophilic activation for vecuronium. Moreover, according to ST and/or BAT cross-reactivity between rocuronium and vecuronium was suspected in 10/14 patients. Except one patient, all patients had negative BAT and ST investigations for atracurium and cisatracurium. Currently, five patients tolerated administration of cisatracurium. All control individuals demonstrated negative ST and BAT for all tested NMBA.

CONCLUSIONS

The BAT constitutes a reliable instrument to diagnose anaphylaxis from rocuronium. The technique also allows quick and simultaneous testing of different potential cross-reactive NMBA and to tailor a safe alternative.

Perioperative anaphylaxis from locally applied rifamycin SV and latex

A patient developed severe anaphylaxis during irrigation of a wound with rifamycin SV. The temporal relationship between application of rifamycin SV, the positive skin test and basophil activation test for rifamycin SV strongly supported diagnosis of anaphylaxis from the locally applied antibiotic. However, after operation the patient had two anaphylactic reactions with pruritus, urticaria and angio-oedema after routine care by a nurse, and these were probably caused by natural rubber latex. This case report has several messages. First, it is not widely appreciated that topically applied drugs and related compounds can elicit life-threatening anaphylaxis. Second, it illustrates patients can present with more than one allergy. Finally, it provides an opportunity to summarize the applications of flow cytometry-assisted quantification of in vitro activated basophils in diagnosing the cause of anaphylaxis during anaesthesia.