Early diagnosis of ataxia-telangiectasia using radiosensitivity testing.

Objectives: To utilize radiosensitivity testing to improve early diagnosis of patients with ataxia-telangiectasia (A-T).

Study Design: We established normal ranges for the colony survival assay (CSA) by testing cells from 104 patients with typical A-T, 29 phenotypic normal patients, and 19 A-T heterozygotes. We also analyzed 61 samples from patients suspected of having A-T and 25 patients with related disorders to compare the CSA with other criteria in the diagnosis of A-T.