Allergy testing: comparison of skin and in vitro tests of allergic reagin.

Skin tests have been used for many years to detect reaginic antibodies in the investigation of allergic patients. Recently in vitro assays of allergic reagins, including the radioallergosorbent test (RAST) and the rat mast cell test (RMCT) have become available. A comparison of the clinical usefulness of these tests suggested that skin tests and the RAST are of comparable diagnostic accuracy and reliability. The RMCT was found to be poorly reproducible and unreliable. For routine cases skin tests should continue to be the procedure of choice. The RAST may reasonably be used when skin tests are unreliable, impractical or contraindicated. The RAST may also be helpful in some cases in resolving discrepancies between skin test results and the clinical history.