Carrier detection in glutaric aciduria type I using interleukin-2-dependent cultured lymphocytes

Summary

Cultured interleukin 2 (IL-2)-dependent leukocytes from 13 patients with glutaric aciduria type I, 12 obligate carriers, 105 family members and 31 normal controls were assayed for glutaryl-CoA dehydrogenase activity. Of the 13 affected patients, 10 (all Ojibway Indian) had residual enzyme activity (2–13% of control) and 3 patients (all non-Indian) had undetectable enzyme activity. There was partial overlap between the distribution of enzyme activity in obligate heterozygotes and in normal controls (mean values±SD: 6.29±0.94 and 10.75±2.58 nmol/h per mg protein respectively). Using an arbitrary cutoff level of <7 nmol/h per mg protein as presumptive evidence of carrier status, the observed frequency of carriers did not differ significantly from that expected from theira priori risk of carrier status. Thirteen per cent of the family members had inconclusive status (activity between 7 and 8.5 nmol/h per mg protein). The method appears suitable for carrier detection, although definitive carrier assignment awaits identification of the mutation(s) responsible for glutaric aciduria type I.