Accuracy in diagnosis of allergy to β-lactams

We have read the interesting paper recently published in Critical Care [1]. In the issue of pharmacodynamics of β-lactams we missed a particular subject: allergy, subtle but sometimes important in intensive and critical care units since clinicians usually manage patients labelled as 'allergic' without having been studied and based only on clinical history [2]. This creates a health resource problem and leads to use alternative treatments in most cases with a higher cost [3].

We would like to contribute in this issue by describing our experience of reaching a reliable diagnosis in subjects assessed for immediate drug allergy reaction (2001 to 2010) [2]. Diagnosis was supported by a skin test [4], and if skin tests were negative by a single-blind drug challenge test [5] (see Table 1). Nursing and physician staff were present with full resuscitation delivery.

Table 1 Diagram for diagnosis of penicillin allergy

The results are shown in Table 2, with 3,426 total studies involving antibiotics, 4,867 drug challenge tests performed, and 159 positive cases (7%) with β-lactams. Only 114 patients were not studied (refusal or rejected). Unquestionably, the most problematic group of antibiotics was penicillins, including aminopenicillins. It is remarkable that 21 patients with a negative skin test suffered a positive oral drug challenge test, more evident in the latter studied period, possibly explained by the lower sensitivity of the skin test for the most currently used aminopenicillins.

Table 2 Data for drug allergy studies 2001 to 2010

Finally, we would like to encourage allergological studies for an accurate diagnosis of drug allergy, a common problem in clinical practice that can influence the decisions on prescription drugs.