In vivo and vitro in diagnosis of latex allergy at Groote Schuur Hospital

OBJECTIVE: The aim of this study was to evaluate the diagnostic utility of skin-prick tests, radio-allergosorbent tests (CAP RASTs), basophil histamine release, sulphidoleukotriene release and Western blotting in the diagnosis of latex allergy at Groote Schuur Hospital. DESIGN: Patients with a history suggesting latex hypersensitivity were recruited via staff health and allergy clinics at Groote Schuur Hospital. A clinical assessment was followed by laboratory investigation and skin-prick testing. A control group consisted of laboratory and hospital staff who had regular latex exposure but were asymptomatic. SETTING: Hospital-based cohort at Groote Schuur Hospital. PARTICIPANTS: Twenty-three patients with suspected latex allergy; 10 control subjects exposed to, but not clinically sensitive to, latex. MAIN OUTCOME: Skin-prick testing was more sensitive than in vitro diagnostic tests for the diagnosis of latex allergy. RESULTS: Eighteen of 21 (85.7%) of the patients tested had a positive skin-prick test with a commercial latex solution (Allerbioprick) and 17/21 (80%) tested skin-prick-positive with an in-house glove extract. CAP RASTs were positive in 13/23 patients (56.5%), sulphidoleukotriene release was positive in 10/23 (43%), histamine release assay was positive in 10/23 (45%) and Western blots were positive in 8/23 (34.7%). All patients with only urticaria were Western blot-negative and CAP RAST-negative, suggesting that they have very little circulating latex-specific IgE. Although patients who were Western blot-positive tended to have multi-organ involvement, both patients with anaphylaxis were Western blot-negative. CONCLUSION: Latex allergy is a significant clinical problem at Groote Schuur Hospital. Titrated skin-prick testing performed in a controlled environment can safely and reliably confirm the diagnosis in patients who do not give a history of anaphylaxis. The CAP RAST was the most sensitive in vitro test for latex allergy locally available, but lacks sensitivity in patients presenting with urticaria only.