Pitfalls in the diagnosis of latex allergy.
BACKGROUND
Screening patients for latex allergy prior to surgery is an important but intensive procedure. The appropriate testing strategy for diagnosing latex (Hevea brasiliensis) allergy involves in-vitro specific IgE or skin prick testing. The sensitivity and specificity of both tests are influenced by patient-specific factors or manufacturing processes that alter the clinically relevant allergens in skin testing solutions.


METHODS
Total IgE and latex-specific IgE testing was introduced as a screening test. Skin prick testing was done on patients with a high probability of latex allergy and negative specific IgE with total IgE <100 kU/L. SDS-PAGE was done on the non-ammoniated latex (NAL) and newly introduced ammoniated latex (AL) reagents for the clinically relevant allergens.


RESULTS
51 patients had a total IgE <100 (range, 2.8-99.0 kU/L), and 10% had a positive skin test. 60% of positive skin tests would have been missed with lower total IgE cut-offs of 50 kU/L (6% of referrals). SDS-PAGE of the NAL solution showed 3 prominent bands with molecular weights of approximately 20, 24 and 42 kDa that correlated with Hev b 6, Hev b 3 and Hev b 7/13, respectively. In contrast, the AL solution showed 3 very faint higher molecular weights bands that did not correlate with clinically relevant antigens.


CONCLUSIONS
Increasing the cut-off value of total IgE for allergen-specific IgE testing increased the sensitivity of the specific IgE test. The NAL reagent had a greater number of clinically significant allergens at higher concentrations than AL, which may have implications for the clinical sensitivity of the newer AL reagent.
Khan
Sujoy
S
Path Links Immunology, Scunthorpe General Hospital, Scunthorpe, United Kingdom; Department of Immunology, Hull Royal Infirmary, University of Hull, Hull, United Kingdom. Electronic address: sujoykhan@gmail.com.
Holding
Steve
S
Department of Immunology, Hull Royal Infirmary, University of Hull, Hull, United Kingdom; Post graduate Medical Institute, University of Hull, Hull, United Kingdom.
Doré
Philip
P
Department of Immunology, Hull Royal Infirmary, University of Hull, Hull, United Kingdom; Hull York Medical School, University of Hull, Hull, United Kingdom.
Sewell
Carrock
C
Path Links Immunology, Scunthorpe General Hospital, Scunthorpe, United Kingdom; Hull York Medical School, University of Hull, Hull, United Kingdom.
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000485:Allergens / Q000276:immunology / Q000378:metabolism / Q000627:therapeutic use; D052179:Antigens, Plant / Q000276:immunology / Q000378:metabolism / Q000627:therapeutic use; D003951:Diagnostic Errors / Q000517:prevention & control; D028482:Hevea; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology / Q000378:metabolism*; D007167:Immunotherapy; D020315:Latex Hypersensitivity / Q000175:diagnosis* / Q000276:immunology / Q000628:therapy; D008875:Middle Aged; D010940:Plant Proteins / Q000276:immunology / Q000378:metabolism / Q000627:therapeutic use; D012015:Reference Standards; D012680:Sensitivity and Specificity; D012698:Serologic Tests / Q000592:standards; D012882:Skin Tests
D000485:Allergens; D052179:Antigens, Plant; C097982:Hev b 6.01 protein, Hevea brasiliensis; D010940:Plant Proteins; C113002:allergen Hev b 7; C061477:REF protein, Hevea brasiliensis; D007073:Immunoglobulin E