Indication
The two most commonly used methods of confirming allergen sensitization are skin testing and allergy blood testing. Both methods are recommended by the NIH guidelines and have similar diagnostic value in terms of sensitivity and specificity.
Advantages of the allergy blood test range from: excellent reproducibility across the full measuring range of the calibration curve, it has very high specificity as it binds to allergen specific IgE, and extremely sensitive too, when compared with skin prick testing. In general, this method of blood testing (in-vitro, out of body) vs skin-prick testing (in-vivo, in body) has a major advantage: it is not always necessary to remove the patient from an anthihistamine medication regimen, and if the skin conditions (such as eczema) are so widespread that allergy skin testing cannot be done. Allergy blood tests, such as ImmunoCAP, are performed without procedure variations, and the results are of excellent standardization.
Adults and children of any age can take an allergy blood test. For babies and very young children, a single needle stick for allergy blood testing is often more gentle than several skin tests. However, skin testing techniques have improved. Most skin testing does not involve needles and typically skin testing results in minimal patient discomfort.
Drawback to RAST and ImmunoCAP techniques do exist. Compared to skin testing, ImmunoCAP and other RAST techniques take longer to perform and are less cost effective. Several studies have also found these tests to be less sensitive than skin testing for the detection of clinically relevant allergies.
In the NIH food guidelines issued in December 2010 it was stated that “The predictive values associated with clinical evidence of allergy for ImmunoCAP cannot be applied to to other test methods.” With over 4000 scientific articles using ImmunoCAP and showing its clinical value, ImmunoCAP is perceived as “Gold standard” for in vitro IgE testing
Read more about this topic: RAST Test
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