Author(s): Zinn C, Lopata A, Visser M, Potter PC
OBJECTIVE: The aim of this study was to assess the spectrum of allergy to South African bony fish (Class Teleosti), crustaceans and molluscs and to confirm or refute suspected allergy, specifically to bony fish, by double-blind, placebo-controlled food challenge (DBPCFC).
DESIGN: Patients were recruited by means of a seafood allergy questionnaire. Subjects with reported allergy to hake, yellowtail, salmon and mackerel were investigated by means of skin-prick tests, RASTs and Western blot analysis. For those subjects with test results that were either all negative or equivocal, a definitive diagnosis of clinical sensitivity was made on the basis of DBPCFC.
SETTING: Volunteer population-based cohort in the Western Cape.
PARTICIPANTS: 105 volunteer subjects with suspected fish allergy were recruited by advertising in the local press.
MAIN OUTCOME: Species-specific bony fish allergy was confirmed or refuted by DBPCFC.
RESULTS: The four most common seafood species reported to cause adverse reactions were prawns (46.7%), crayfish (43.8%), abalone (35.2%) and black mussels (33.3%). The four most common bony fish species to cause reactions were hake (24.8%), yellowtail (21.9%), salmon (15.2%) and mackerel (15.2%). Seven DBPCFCs were performed and two open challenges. Skin-prick tests produced one false-negative result. Western blots produced one false-negative and one false-positive result. The RAST had a 100% correlation with DBPCFC.
CONCLUSIONS: Local bony fish represent a significant cause of clinical reactions to seafood in the Western Cape. Although skin-prick tests, RASTs and Western blotting tests assist in the documentation of an IgE responder state, confirmation of clinical sensitivity can only be made with certainty by means of DBPCFC.