Table 2.

Questions left unanswered about IgE deficiency.

What we don't know about IgE deficiency: •It is unclear how many IgE deficient individuals have truly absent IgE in the serum, compared with those who have very low IgE levels, but close to the limits of IgE detection in the blood. •There is, therefore, a need to introduce more precise IgE measurements in the clinical practice, at levels <2 kU/L. •If so, what exactly is the genetic defect resulting in IgE deficiency? •Consequently, is there a familial component of IgE deficiency? •At what point in lifetime might individuals become IgE deficient, and how is this related to cancer occurrence? •What are the full clinical characteristics of patients with IgE deficiency ?

What we don't know about IgE deficiency and cancer: •Is cancer causative to IgE deficiency, or vice versa: Does IgE deficiency reflect an immunomodulatory response resulting in cancer? •Would it be useful to introduce evaluation for IgE deficiency as a routine test in clinical practice? •What would be the ethical implications of predicting the cancer risk in patients who have their IgE levels checked for allergy diagnosis? •Is there any role for performing allergy skin tests as part of the oncology screening in IgE deficient individuals? •Many of these questions could be answered by multicenter longitudinal studies following the IgE levels and cancer prevalence/progression