Adjusted carrier risk assessment estimates have been previously published based on aggregate results of several studies.15 16 These estimates calculate the probability of being an SMA carrier when an individual without a family history of SMA receives a test result showing two or more SMN1 copies. These calculations account for rare mutations undetectable by the method described here, and model the “2+0” carrier genotype. Adjusted carrier risk was calculated for each ethnic group based on its unique allele frequencies (table 4). The result for the Caucasian population (1:632) is similar to that previously reported by Smith et al (1:648).16 In that report calculations were based on data from a compilation of studies from countries in Europe, USA, and Australia. The adjusted risk estimate in the Ashkenazi Jewish population (1:350) is approximately two times higher than the Caucasian group because of the higher frequency of two-copy alleles. As expected, the unusually high frequency of two-copy alleles in the African American population produces an adjusted risk factor more than five times greater than that of Caucasians or Asians. Additionally, a “3+0” genotype
