- If screen values do not meet the absolutely exclusionary values given below but are still outside the normal reference range, treatment for folic acid/B12 deficiency or thyroid disorder, as appropriate, may be initiated or adjusted with re-evaluation of the subject within three months. Within these three months of treatment, the subject's cognitive condition must be clinically unchanged or worse for the subject to be acceptable. Once accepted, the subject must remain on the appropriate treatment throughout the study.