Patients with drug reactions -- is it worth testing?

BACKGROUND

Unevaluated drug reactions that lead to the prescription of expensive alternative medication is the reason why the European Academy of Allergy and Clinical Immunology guidelines recommend verification. We evaluated whether a structured test procedure in patients with drug reactions is worth the potential risk.

METHODS

We retrospectively analysed the charts of a cohort of 291 (220 females/71 males) consecutive patients from January 2003 to June 2004, who presented at the department's allergy outpatient clinic with histories of drug reactions. Twenty-three patients reported more than one independent episode resulting in 325 cases. All patients underwent the following procedure: (1) detailed history; (2) skin test and/or beta-lactam-specific IgE and; (3) if inconclusive, each patient was offered provocation testing -- if needed with alternative medication.

RESULTS

We evaluated reactions to 130 antibiotics, 90 to nonsteroidal anti-inflammatory drugs, 36 to local anaesthetics and 69 to other drugs. An association between drug intake and reaction was confirmed in 100 and excluded in 157 cases. Fourteen of 104 drug provocation tests (DPT), among these four reactions to placebo, yielded positive results but were managed without difficulty. In 68 cases, the procedure remained inconclusive. Additionally, we recommended 197 safe alternative regimens to 85 patients. Overall, our test procedure resulted in clear-cut recommendations to 82.1% (239/291) of the patients.

CONCLUSIONS

A standardized work-up including DPTs in patients with drug reactions leads to clear-cut advice concerning future tolerability or avoidance of certain drugs including recommendations for alternative medication in the vast majority of patients at the cost of only a low risk of mild side effects.

The performance of a component-based allergen-microarray in clinical practice

BACKGROUND

Currently, the diagnosis of IgE-mediated allergy is based on allergen-specific history and diagnostic procedures using natural allergen extracts for in vivo and in vitro tests.

OBJECTIVE

The aim of the study was to comparatively analyse a new component-based allergen-microarray and the 'quasi-standard' ImmunoCAP for their clinical relevance in patients with allergic rhinoconjunctivitis to five aeroallergens [house dust mite (HDM), cat dander, birch, grass and mugwort pollen] in a prospective, double-centre study.

METHODS

We enrolled 120 subjects at the two study centres. Allergic patients were defined as having an allergen-specific history plus a concomitant positive skin-prick test (SPT) to natural allergen extracts and specific serum IgE was measured by both methods. Each allergen was analysed separately.

RESULTS

The microarray performed equally well in receiver-operating characteristic curve (ROC) analyses when compared with the CAP in cat (23 allergic vs 97 non-allergic, ROC area under the curve microarray 0.950 vs CAP 0.894, P = 0.211), birch (31/89, 0.908 vs 0.878, P = 0.483) and grass pollen (47/73, 0.923 vs 0.915, P = 0.770). It was slightly less sensitive in HDM-allergic subjects (26 allergic vs 94 non-allergic, ROC area microarray 0.808 vs CAP 0.911, P = 0.053) and displayed a reduced sensitivity in the mugwort pollen-allergic patients (17/103, 0.723 vs 0.879, P = 0.032).

CONCLUSIONS

Component-based testing and the whole-allergen CAP are equally relevant in the diagnosis of grass-, birch- and cat-allergic patients. Although slightly less sensitive, the microarray is sufficient for the diagnosis of HDM-allergic patients, but needs alternative and/or additional components for detecting mugwort allergy.