Table 4.
Clinically Useful Predictors of Outcome
| Parameter | Outcome | Sensitivity | Specificity |
|---|---|---|---|
| Onset > 4 months | Attenuated mild | 47% | 100% |
| Onset 1st week | Severe | 87% | 70% |
| CSF glycine > 230 μM | Severe | 43% | 100% |
| CSF:plasma glycine ratio ≤ 0.08 | Attenuated | 28% | 100% |
| Brain malformation severe | Severe | 29% | 100% |
| Brain malformation all (including HCC) | Severe | 71% | 92% |
| No epilepsy (no AEDs) | Attenuated | 70% | 100% |
| Glycine index > 3a | Severe | 87% | 100% |
| 2 nonmissense mutations | Severe | 36% | 95% |
| Mutation scoreb = −2 | Severe | 59% | 97% |
| Mutation scoreb ≥ 1 | Attenuated | 76% | 94% |
a
A glycine index of 3 mmol/kg/day for a child on breast milk or regular infant formula with intake of 150 ml/kg/day calculates to a sodium benzoate dose of 510–540 mg/kg/day to bring glycine levels within therapeutic range (120–300 μM).
b
The mutation score provides a score of −1 for a mutation expected to leave no residual activity and +2 for a mutation that is expected to have residual activity. The sum of both alleles scored as is currently known is used.
AED = antiepileptic drug; CSF = cerebrospinal fluid; HCC = hypoplastic corpus callosum.