A diagnosis of Job Syndrome can initially be made based on a clinical evaluation, including a detailed patient history and identification of the disorder’s characteristic findings. However, genetic testing will more accurately reveal the presence of the STAT3 mutation. 

In addition, lab tests that may help with such a diagnosis. They include blood tests that demonstrate elevated levels of IgE in the blood and elevated levels of certain white blood cells known as eosinophils (eosinophilia). IgE levels may drop to normal or near normal levels in adulthood and, therefore, normal IgE levels in an adult do not necessarily rule out a diagnosis of Job Syndrome.

X-ray studies such as computed tomography (CT scanning) can be taken to detect lung infections and the development of pneumatoceles within the lungs, which is a key indicator of Job Syndrome.

A scoring system was devised by researchers at the National Institutes of Health (NIH) to help with the diagnosis of Job Syndrome. It addresses several clinical findings using a points system, zero meaning none or absent, and 10 meaning severe. It looks at a patient’s IgE levels, skin abscesses, the presence of pneumonias, rashes, eczema, sinusitis, and more.