The association of food anaphylaxis in antiphospholipid syndrome and thrombosis cannot be considered a coincidence

Introduction

To the Editor, We have read with great interest the comments on our study “Food anaphylaxis in antiphospholipid syndrome and thrombosis.¹ We are very grateful to the authors for the opportunity that our colleagues bring us to clarify some details. Severe anaphylaxis, fortunately, is an uncommon disease. The actual incidence of anaphylaxis is unknown but is estimated to be 10 to 20/100,000 patients/year. The biggest study on anaphylaxis among hospitalised patients in the previous decade was conducted as a retrospective study of adult patients between 1992 and 2001 at a tertiary care centre in Bangkok. Of 448,211 admissions, 80 events of anaphylaxis in 79 patients (0.017%) were found.² So, it was very difficult to find a big sample to anaphylaxis due to seed or fruit. We had to revise the records of 21,879 patients admitted to our Allergy Department in the last 22 years to find the number of patients necessary for a good statistical analysis. The sample size was calculated by simple random sampling in a control:case ratio of 1, with confidence limits of 98%, a power of 90% and an average of exposition among controls of 25%. A stratified analysis was performed in order to estimate the confounding and artefactual factors among the different independent variables, avoiding the selection bias. We finally selected 52 patients who suffered from severe anaphylaxis and 28% of them had anticardiolipin antibodies and 17.3% had thrombosis. This percentage can be considered not too big, but the fact that 75% of patients’ diagnoses as having antiphospholipid...