There are several scoring methods for interpreting the results of a radioallergosorbent test (RAST). One of the most commonly used is the CAP (College of American Pathologist) scheme employed with Pharmacia Diagnostics.
This is a quantitative assay that is standardized against the WHO IgE standard.
IgE Concentration
Interpretation
Class of Response
0 to 0.34 kU/L
negative or undetectable
0
0.35 to 0.70 kU/L
borderline or equivocal
1
0.71 to 3.50 kU/L
positive, moderate
2
3.51 to 17.50 kU/L
positive, high
3
17.51 to 50.00 kU/L
positive, very high
4
50.01 to 100.00 kU/L
positive, very high
5
> 100.00 kU/L
positive, very high
6
where:
• 1 IU/mL (or 1 kU/L) IgE is equivalent to 2.4 ng/mL (or µg/L)
• The Pharmacia CAP System is an alternative scoring system that reports fluorescent results relative to a standard.
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