BACKGROUND Patients with primary antibody deficiency often have delayed diagnosis. Very low IgE, found during investigations for allergy, may be a marker for other immunodeficiency. METHODS We introduced a new laboratory policy of testing cases with very low IgE levels for possible linked antibody deficiency. The data represent an audit of routine results collected over two years. RESULTS Very low IgE (≤2 IU/mL) was identified in 85/2622 (3.2%) routine patient samples. Two children and four adult patients were found to have one or more classes of immunoglobulin below the reference range for age. In 2/6, the initiative of the laboratory led to a new unsuspected diagnosis of antibody immunodeficiency. CONCLUSIONS Common variable immunodeficiency continues to be overlooked as a primary cause of lung disease in adults. Very low serum IgE should trigger appropriate investigation (immunoglobulin quantification and serum electrophoresis).