A RAST test (short for radioallergosorbent test) is a blood test used to determine to what substances a person is allergic. This is different from a skin allergy test, which determines allergy by the reaction of a person's skin to different substances.
Picture courtesy: http://www.allergyfreemom.com/Allergy_Testing.php
CAP RAST, CAP FEIA (fluorenzymeimmunoassay) is a more superior test
This new test has replaced the original RAST in approximately 80% of the world's commercial clinical laboratories, where specific IgE testing is performed. The newest version, the ImmunoCAP Specific IgE 0-100, is the only specific IgE assay to receive FDA approval to quantitatively report to its detection limit of 0.1kU/l.
The RAST test is scored on a scale from 0 to 6:
| RAST rating | IgE level (KU/L) | comment |
|---|---|---|
| 0 | < 0.35 | ABSENT OR UNDETECTABLE ALLERGEN SPECIFIC IgE |
| 1 | 0.35 - 0.69 | LOW LEVEL OF ALLERGEN SPECIFIC IgE |
| 2 | 0.70 - 3.49 | MODERATE LEVEL OF ALLERGEN SPECIFIC IgE |
| 3 | 3.50 - 17.49 | HIGH LEVEL OF ALLERGEN SPECIFIC IgE |
| 4 | 17.50 - 49.99 | VERY HIGH LEVEL OF ALLERGEN SPECIFIC IgE |
| 5 | 50.0 - 100.00 | VERY HIGH LEVEL OF ALLERGEN SPECIFIC IgE |
| 6 | > 100.00 | EXTREMELY HIGH LEVEL OF ALLERGEN SPECIFIC IgE |
This new test has replaced the original RAST in approximately 80% of the world's commercial clinical laboratories, where specific IgE testing is performed. The newest version, the ImmunoCAP Specific IgE 0-100, is the only specific IgE assay to receive FDA approval to quantitatively report to its detection limit of 0.1kU/l.
The guidelines for diagnosis and management of food allergy issues by the National Institute of Health state that:
"sIgE levels were originally measured using the radioallergosorbent test (RAST), but this test has been replaced by more sensitive fluorescence enzyme-labeled assays and the term RAST should be abandoned
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