The following information may help to address your question:
Eight or more ear infections
Two or more cases of pneumonia
Infections that do not resolve with antibiotic treatment for two or more months
Failure to gain weight or grow normally
Infections that require intravenous antibiotic treatment
Deep-seated infections, such as pneumonia that affects an entire lung or an abscess in the liver
Persistent thrush in the mouth or throat
A family history of immune deficiency or infant deaths due to infections
Diagnosis can be confirmed by blood tests. Blood tests show significantly lower-than-normal levels of T cells and antibodies.
For further details on diagnosis see the following Web pages:
The Primary Immunodeficiency Resource Center provides further details regarding diagnosis of SCID. Click on the embedded link to view the page.
An article from Medscape Reference provides detailed information on the diagnosis of SCID. Click on eMedicine Journal to view the page. You may need to register to view the article, but registration is free.