TABLE 1.
Neural tube defect (NTD) risk category by red blood cell (RBC) folate concentrations for different blood folate assay methods1
| Risk category | NTD prevalence per 10,000 live births2 |
RBC folate concentration (nmol/L) | |
|---|---|---|---|
| Molloy method | Pfeiffer/NHANES method3 |
||
| High | >14 | ≤699 | ≤585 |
| Elevated | 9 – 14 | 700 – 905 | 586 – 747 |
| Optimal | 4 – <9 | 906 – 1499 | 748 – 1215 |
| Limited additional benefit | Outside of estimable range | ≥1500 | ≥1216 |
1
Derived from Crider et al., 2014 (1) and Daly et al., 1995 (2)
2
NTD prevalence estimates are based on the median estimated NTD prevalence for an entire population with a given RBC folate concentration, corresponding to the risk category cut points; rounded to the nearest whole number
3
To convert from Molloy method to Pfeiffer/NHANES method, the following conversion formula should be used: Pfeiffer/NHANES RBC folate [nmol/L] = (Molloy RBC folate [nmol/L] * 0.7876) + 34.2802 [nmol/L] (1)