[Sensible diagnosis in suspected immune deficiency].

Patients reporting a marked proclivity for developing infections often present the care-providing physician with a diagnostic problem. If the available diagnostic possibilities are to be used rationally and with proper understanding, a thorough knowledge of the nature of an immune reaction is essential. The present paper contains a step-by-step scheme that may serve as an aid for the diagnostic approach. In addition to the clinical examination and routine laboratory investigations, simple tests such as Mérieux multitest and serum antibody titer serve to orientate the doctor on the patient's immune status. More sophisticated time-consuming and expensive tests, such as flow cytometric analysis of immune cells or functional in vitro investigations permit the identification of immune deficiency syndromes. These tests should, however, be undertaken only when severe immunodeficiency is suspected clinically or the orienting studies make it appear likely.