ERYTHROCYTE FOLATE ANALYSIS - A CAUSE FOR CONCERN

Neural tube defects tan be prevented by adequate intake of periconcept ional folate, and inverse associations between folate status and cardi ovascular disease and various cancers have been noted. Thus, there is renewed interest in the analysis of red cell folate (RCF) as an indica tor of folate deficiency risk. Assessment of the assumptions that unde rpin RCF assays indicates that many are false. Published literature su ggests that increased deoxy-hemaglobin (which can bind RCF electrostat ically) yields more assayable folate, and increased oxy-hemoglobin (wh ich cannot bind RCF) yields less assayable folate. It is argued that a s deoxy-hemoglobin picks up oxygen and switches quaternary structure, any bound folate must, on purely theoretical grounds, become physicall y ''trapped''. Venous blood taken for analysis is 65% to 75% saturated with oxygen, and pro-rata ''trapping'' will lead to serious underesti mation of RCF. Hence, doubt is cast over the validity of all previous RCF values. Some strategies for accurately assessing RCF are suggested .