Percentage of false positives and false negatives w RAST
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Percentage of false positives and false negatives w RAST
How often to false positives and false negatives occur with the RAST food allergy blood test? When a retest is done several months later, will the same false results appear, or is there a chance an entirely new set of false results may crop up?
Last edited by VintageMom on Wed Feb 22, 2012 8:43 pm, edited 1 time in total.
- Dr Adam Fox
- Posts: 72
- Joined: Thu Feb 17, 2011 12:04 am
Re: Percentage of false positives and false negatives w RAST
RAST (or specific IgE tests) are reliable when interpreted carefully in the context of a clinical history. They simply can't be used a 'yes' or 'no' tool to tell you what you are allergic to. As mentioned in a previous response, it is key that they are interpreted by a doctor with appropriate experience at doing so.
Dr Adam Fox
MA(Hons), MD, MSc, MB, BS, DCH, FRCPCH, FHEA, Dip Allergy
http://www.talkhealthpartnership.com/on ... am_fox.php
MA(Hons), MD, MSc, MB, BS, DCH, FRCPCH, FHEA, Dip Allergy
http://www.talkhealthpartnership.com/on ... am_fox.php
- mark
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- Location: Hampshire
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Contact: Contact mark
Re: Percentage of false positives and false negatives w RAST
delayed reactions are easily missed. would you agree the Elise test followed by ACT/ DTH would be a good way to track down the culprits?
Mark Westbrook
Fitness Consultant
Freelance
http://www.talkhealthpartnership.com/bl ... arks-blog/
Fitness Consultant
Freelance
http://www.talkhealthpartnership.com/bl ... arks-blog/
- Dr Stephen Till
- Posts: 11
- Joined: Fri Feb 17, 2012 2:06 pm
Re: Percentage of false positives and false negatives w RAST
As far as I am aware such tests are not used in our routine clinical practice.
Dr Stephen Till
Consultant in Adult Allergy, Guy's and St Thomas' NHS Foundation Trust
Consultant in Adult Allergy, Guy's and St Thomas' NHS Foundation Trust
- mark
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- Joined: Fri Nov 13, 2009 12:38 pm
- Location: Hampshire
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Contact: Contact mark
Re: Percentage of false positives and false negatives w RAST
oh ok what would you suggest as a good journey to source the culprits.
Mark Westbrook
Fitness Consultant
Freelance
http://www.talkhealthpartnership.com/bl ... arks-blog/
Fitness Consultant
Freelance
http://www.talkhealthpartnership.com/bl ... arks-blog/
- Dr Helen Brough
- Posts: 52
- Joined: Wed Feb 16, 2011 3:36 pm
Re: Percentage of false positives and false negatives w RAST
Dear Mark,
Specific IgE tests are not good at testing for delayed allergies as these are not usually IgE mediated. They are usually T cell mediated. The same goes for skin[ prick tests. There are some tests for delayed allergies including patch testing for food (although there is conflicting evidence on this). For contact allergies such as nickel and other chemicals patch testing is much more reliable. Delayed intradermal testing is sometimes used for delayed reactions to drugs but not for foods.
In paediatrics (which is what I mainly practice) most of the delayed allergies for foods giving to rise to gastrointestinal symptoms or eczema are assessed by removing the considered offending food from the diet strictly for 4-6 weeks followed by reintroduction. This most by done under dietetic supervision.
Kind regards,
Specific IgE tests are not good at testing for delayed allergies as these are not usually IgE mediated. They are usually T cell mediated. The same goes for skin[ prick tests. There are some tests for delayed allergies including patch testing for food (although there is conflicting evidence on this). For contact allergies such as nickel and other chemicals patch testing is much more reliable. Delayed intradermal testing is sometimes used for delayed reactions to drugs but not for foods.
In paediatrics (which is what I mainly practice) most of the delayed allergies for foods giving to rise to gastrointestinal symptoms or eczema are assessed by removing the considered offending food from the diet strictly for 4-6 weeks followed by reintroduction. This most by done under dietetic supervision.
Kind regards,
Dr Helen Brough
Consultant in Paediatric Allergy
Guy's & St. Thomas' NHS Foundation Trust
http://www.talkhealthpartnership.com/on ... brough.php
Consultant in Paediatric Allergy
Guy's & St. Thomas' NHS Foundation Trust
http://www.talkhealthpartnership.com/on ... brough.php