Laboratory screening for the diagnosis of children with primary immunodeficiencies.

To select simple and low-cost laboratory tests that contribute to the diagnosis of primary immunodeficiencies (PID) in children, the medical records of 98 patients with PID were analyzed. White blood cell counts, serum IgG, IgM and IgA determinations, Shick test, isohemagglutinin titers, delayed cutaneous hypersensitivity tests, nitro blue tetrazolium test and hemolytic complement (CH50) determination associated with clinical data led to the diagnosis in 95% of cases. Applying this laboratory screening to patient series studies in other countries, the diagnosis was suggested in at least 92% of the cases. This screening proposal may be used as a guideline in the standardization of complementary tests for the diagnosis of immunodeficiencies in pediatric centers of developing countries and also at the primary medical care level in developed countries.