D3.264 - Pioneering study evaluating the Basophil Activation Test (BAT), PENFAST and skin sensitization to penicillin in patients with gestational syphilis

Less than 10% of individuals reporting allergy to beta-lactams after investigation with allergy tests are truly allergic. However provocation tests with pregnant women and a history of anaphylaxis are contraindicated and skin tests with penicillin G show low sensitivity. BAT can be an important tool for identifying allergies, avoiding the risk of reaction upon provocation and unnecessary desensitization due to the use of Benzathine penicillin in the treatment of gestational syphilis. Objective: To describe results of risk factors for reactions to penicillin, using PENFAST, results of skin tests and BAT in pregnant women with syphilis referred for desensitization

Information was collected from medical records, skin tests were carried out with Penicillin G potassium, following the ASBAI and Ministry of Health protocol and EAACI standardization. The BAT was performed according to the supplier's instructions with benzathine penicillin

Among the pregnant women who were desensitized, three underwent BAT. One patient had a maximum PENFAST score, a positive intradermal test (increase greater than twice the initial papule), with a positive BAT test. Another scored 3 on PENFAST, negative skin test and negative BAT. A third pregnant woman had two previous episodes of anaphylaxis, PENFAST of 5, negative skin test and positive BAT. 

The BAT associated with the severity of reactions was more sensitive in this group of patients when compared to skin tests. More than 95 pregnant patients in our service have been desensitized to date, but the skin test showed low sensitivity (7.6%) associated with the desensitization reaction. We believe that BAT can help to better identify allergic patients, avoiding the risk of reactions to unnecessary provocations and desensitization.