From the Guidelines
Systemic steroid use does not significantly affect RAST panel results, as these tests measure specific IgE antibodies in the blood, which are not directly influenced by steroid medications. Unlike skin prick tests, which can be suppressed by antihistamines and steroids, RAST panels can be performed without concern for false negative results in patients taking oral or injectable steroids such as prednisone, methylprednisolone, or dexamethasone 1. The reason for this difference is that systemic steroids work primarily by reducing inflammation and immune cell activity, but they do not rapidly eliminate existing IgE antibodies from circulation that the RAST test measures.
Some key points to consider when interpreting RAST panel results in patients on systemic steroids include:
- The effect of systemic steroids on weaker reactions has not been assessed, but clinical experience suggests that if the daily dose is no higher than 10 mg prednisolone, suppression of positive patch tests is unlikely 1.
- Long-term steroid use (months to years) might potentially reduce overall IgE production, but this effect is generally not significant enough to invalidate test results in most clinical scenarios.
- Patients can continue taking oral or injectable steroids while undergoing RAST testing without concern for false negative results, which is an advantage of blood-based allergy testing over skin testing in patients who cannot temporarily discontinue their steroid therapy.
It's also worth noting that guidelines for discontinuation of medications that might interfere with interpretation of oral food challenge testing suggest that oral/intramuscular/intravenous steroids should be discontinued 3 days to 2 weeks before the test, depending on the specific medication and dose 1. However, this guideline is based on concerns regarding the potential for suppression of late-phase responses and does not apply to RAST panel testing. In general, patients can continue taking systemic steroids while undergoing RAST testing, and the results are unlikely to be significantly affected.
From the Research
RAST Panels and Systemic Steroid Use
- The effect of systemic steroid use on RAST (RadioAllergoSorbent Test) panels is not directly addressed in the provided studies, but we can look at the relationship between steroid use and allergy testing in general.
- A study from 1996 2 found that long-term oral corticosteroid therapy does not alter the results of immediate-type allergy skin prick tests, suggesting that systemic steroid use may not affect the results of allergy tests.
- However, this study focused on skin prick tests, not RAST panels specifically.
- Another study from 1985 3 compared the results of RAST, IgE FAST, and prick-puncture methods, but did not investigate the effect of systemic steroid use on these tests.
- There is no direct evidence in the provided studies to suggest that systemic steroid use affects RAST panels, but it is possible that the results of RAST panels could be influenced by steroid use, as steroids can modulate the immune system.
Allergy Testing and Steroid Use
- A study from 2015 4 investigated skin testing for immediate hypersensitivity to corticosteroids and found that skin tests can provide sufficient evidence to diagnose allergy in patients with a clear history of immediate hypersensitivity to corticosteroids.
- This study suggests that steroid use can be associated with allergic reactions, but does not provide information on the effect of systemic steroid use on RAST panels.
- Overall, while there is no direct evidence to answer the question, the provided studies suggest that systemic steroid use may not significantly affect the results of allergy tests, including RAST panels 2, 3. However, more research is needed to confirm this.