Use of the Basophil Activation Test May Reduce the Need for Drug Provocation in Amoxicillin-Clavulanic Allergy.

BACKGROUND

Reports of selective reactions to clavulanic acid (CLV) have increased in recent decades because of its increased prescription in combination with amoxicillin (AX) as AX-CLV. Basophil activation test (BAT) is used for diagnosing beta-lactam immediate hypersensitivity and is the only available in vitro assay for diagnosing patients with immediate hypersensitivity to CLV. However, few studies, and with limited numbers of patients have been published.

OBJECTIVE

The aim of this study was to establish the sensitivity, specificity, and negativization rates of BAT to AX and CLV.

METHODS

We studied 115 patients with immediate allergic reactions after AX-CLV treatment, 57 with selective reactions to AX (group A), 58 with selective reactions to CLV (group B), and 28 tolerant subjects. BAT was performed with AX in group A and with CLV in group B. A 4-year follow-up study was performed in patients with an initial positive BAT result.

RESULTS

The overall sensitivity of BAT was 55%, specificity 89%, and positive predictive value (PPV) 96%. For group A, sensitivity was 47%, specificity 93%, and PPV 93%; for group B, sensitivity was 62%, specificity 89%, and PPV 92%. Follow-up study showed a faster negativization rate of BAT for group A, with around 40% of patients becoming negative at 12 months in both groups.

CONCLUSIONS

The high PPV of BAT to CLV shows its potential value as a complementary tool to the allergological workup of patients with immediate allergic reactions after AX-CLV treatment. Importantly, the assay should be done within the first 12 months after the reaction to reduce false-negative results.