Allergic reactions to peanuts can be fatal.
And peanut allergies affect around 1 in 55 people in the UK. (Around 2%)
The good news is that Santos et al (2018) introduced a new candidate test for peanut allergy based on human mast cell activation.
The ROC curve for the new test looks pretty impressive: the ROC AUC = 0.87 with a best-case scenario giving a sensitivity and specificity of 100% and 87% for severe peanut allergies.
So far, so good.
The trouble is that with a prevalence of just 2%, the False Alarm rate is likely to be rather high. More than half of all positive tests will be false positives.