[When should immunologic explorations be carried out in children with suspicion of primary immunodeficiency?].

The identification of primary immunodeficiency is important in the prognosis and treatment of patients with these rare genetic diseases. For their diagnosis, simple screening explorations need to be carried out in case of severe, recurrent, and/or unusual infections. These include the whole blood cell count, plasmatic immunoglobulin levels, and postimmunization and/or post-infectious serologies. These examinations are used to guide the diagnosis with the joint analysis of patient's medical history, the clinical examination, and screening of biological results. They will then guide the prescription of more specific second-line explorations depending on the type of primary immunodeficiency suspected.