A comparative study of the tryptase release test and the cellular allergen stimulation test (CAST) in mite sensitive patients.
BACKGROUND
The stimulation of blood basophils to release mediators in vitro is widely used for diagnosis of allergic diseases. Tryptase release and sulphidopeptideleukotriene production are both triggered by cross-bridging of adjacent IgE molecules on the surface of IgE-bearing basophils.


OBJECTIVE
We have compared the sensitivity of tryptase release test (TRT) and cellular allergen stimulation test (CAST) which, respectively, measure tryptase and sulphidopeptideleukotrienes that are produced upon cell stimulation by mite extracts.


METHODS
Blood was taken from 247 patients with allergy to mites and 137 non-allergic control subjects. We measured tryptase release from basophils after allergen challenge in vitro by sandwich radioimmunoassay. The sulphidopeptideleukotrienes production was quantified by an ELISA test based on a monoclonal antibody which recognized leukotriene T4 (LTC4) and its metabolites LTD4 and LTE4.


RESULTS
Our data show that both methods are equally effective to distinguish allergic patients from normal controls (P > 0.0001). There was a significant correlation between mite-specific serum IgE and CAST results (r = 0.69 for Dermatophagoides pteronyssinus; r = 0.73 for Dermatophagoides farinae). Correlations between IgE against mites and tryptase values appeared rather poor (r = 0.47 for Dermatophagoides pteronyssinus; 0.49 for Dermatophagoides farinae). Moreover, the data were used for the calculation of sensitivity, specificity, prevalence, and overall efficiency (Roc/Galen & Gambino analysis). The results were as follows: 71%, 87%, 64%, 76% (CAST results for Dermatophagoides farinae); 64%, 78%, 53%, 70% (TRT results for Dermatophagoides farinae).


CONCLUSIONS
The partial discrepancies observed could be interpreted as a consequence of conditions that were technically not optimal. False-positive results may be due to the action of some non-specific cytotoxic agent, false-negative results may be due to hyporesponsive basophils or the low number of cells participating in the reaction and finally, in the case of TRT, to G4 monoclonal antibody to tryptase employed.
Allergy Unit, Santissima Trinità Hospital, Fossano, Italy.
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Rossi
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Monasterolo
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Operti
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000918:Antibody Specificity; D001491:Basophils / Q000201:enzymology*; D002648:Child; D053818:Chymases; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000201:enzymology*; D007073:Immunoglobulin E / Q000097:blood; D018836:Inflammation Mediators / Q000097:blood*; D015289:Leukotrienes / Q000097:blood*; D008297:Male; D008875:Middle Aged; D008925:Mites / Q000201:enzymology / Q000276:immunology; D011863:Radioimmunoassay; D012697:Serine Endopeptidases / Q000097:blood*; D018709:Statistics, Nonparametric; D053802:Tryptases
D018836:Inflammation Mediators; D015289:Leukotrienes; D007073:Immunoglobulin E; D012697:Serine Endopeptidases; C083294:chymase 2; D053818:Chymases; D053802:Tryptases