METHODS TO ASSESS RAST RESULTS IN PATIENTS EXPOSED TO CHEMICAL ALLERGENS

PAST is routinely used to assess the presence of IgE antibodies agains t environmental allergens in the sera of symptomatic patients. With ex posure to low-mol.-mass (chemical) allergens, PAST is also done, but t he interpretation of results is more difficult. A study was undertaken to assess methods which have been employed to determine the positivit y of sera and to develop an objective, statistically based procedure f or determination of RAST positivity to chemical allergens. Sera were o btained from 14 nonsensitized (control) subjects and examined for tota l IgE by radioimmunoassay, and for cyanuric chloride (CyCl)-specific I gE by PAST. Linear regression analysis revealed the correlation betwee n the tests to be 0.94. Equations for the 95% and 99% predicted interv als were obtained. Sera from 19 cyanuric chloride workers were tested for total and specific IgE. Positivity of PAST results was determined by three methods: PAST inhibition, PAST ratio (binding to CyCl-human s erum albumin (HSA) disks/HSA disks), and the regression equation where values outside the 99% predicted interval were considered to be posit ive and those >95% <99% were considered to be borderline values. Deter mination of CyCl PAST positivity by the regression method gave results comparable to those obtained from RAST inhibition, whereas the RAST r atio resulted in many more false positive conclusions. This statistica l approach to PAST analysis was also used to assess sera from patients exposed to the unrelated chemical allergens, toluene diisocyanate and formaldehyde. Conclusions based on the regression method were in good agreement with those from PAST inhibition assay. Moreover, use of one standard curve may be sufficient for interpretation of RAST results f or diverse haptenic allergens. These results indicate that the regress ion method provides a statistical basis from which to determine positi vity of PAST analyses while eliminating the need for PAST inhibition a ssays.