Can I trust low-level responses on ISAC?
Answer: Yes, but most low-level result are not associated with clinical symptoms.
Example: A patient with allergy suspicion is tested on ISAC.
Results: Low-level responses (< 1 ISU) is registered. It has been reported that the CV for IgE levels < 1 ISU are high. Can I rely on these low-level results?
Explanation: It has been reported that many low-level results are not associated with clinical symptoms. This may be due to the fact that clinical reaction do not occur until the allergen threshold for clinical symptoms have not been reached for the patient. The allergen load threshold can also be “pushed down” if the patient has an infection, is stressed or exposed to many allergens.
The binding capacity on the glass chip is much lower than for the ImmunoCAP allergen components. All results, and especially low-level results, must be evaluated with extra attention taken to the clinical history. For low-level results (<1 ISU) the CV for ISAC increases significantly. Low-level results should therefore be evaluated with this in mind.
Note also that protein families with very high sequence homology may be used for quality control. Usually the IgE ab level within the entire profilin family, within the entire tropomyosin family, and within most serum albumins are similar. A single low-level profilin/tropomyosin/serum albumin response could be due to background noise and should thus most likely be ignored.
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