EGRAC and erythrocyte riboflavin measurements were conducted within 2 months of each another.
Riboflavin deficiency was defined as EGRAC [greater than or equal to] 1.4 (12), anemia was defined as hemoglobin <110 g/L (21), and iron deficiency was defined as plasma ferritin <12 [micro]g/L.
The log erythrocyte riboflavin concentration was negatively correlated with EGRAC (rz = 0.390; P <0.0001; y = -0.4503x + 5.726 nmol/L; Fig.
As Murphy and Fernandez-Ballart (1) note, our report states that two indices of riboflavin status, erythrocyte glutathione reductase activation coefficient (EGRAC) and plasma riboflavin, deteriorated after the folic acid supplementation regimen.
For this reason, and as has been known for many years, EGRAC is sensitive in the short term to dietary intake of riboflavin (4).
The most common measure of riboflavin status in current use is EGRAC. It is accepted that there is a discrepancy between estimates of riboflavin deficiency through the use of EGRAC and estimates made from dietary intakes, such as to suggest either an overestimate of bioavailability or an inappropriately low EGRAC threshold for normality.
In subsequent analyses, plasma riboflavin, FMN, EGRAC, tHcy, vitamin [B.sub.12], and vitamin [B.sub.6] were log-transformed (base 10) because of skewness.
If EGRAC were used as the measurement of riboflavin status, 52% of the study population would be deemed biochemically riboflavin deficient (EGRAC >1.4).
We investigated the relationship between these analytes and their correlation with EGRAC in healthy elderly individuals.
EGRAC was used to determine vitamin [B.sub.2] status in the study population, and 52 individuals with suboptimal vitamin [B.sub.2] status (EGRAC [greater than or equal to] 1.20) were invited to participate in a 12-week randomized, double-blind, placebo-controlled, low-dose riboflavin intervention.
EASTAC (28) and EGRAC (29) were measured by enzyme assay on the Cobas Fara centrifugal analyzer (Roche Diagnostics).
There was no significant seasonal variation in the status of vitamin [B.sub.6] (EASTAC), serum vitamin [B.sub.12], or riboflavin (EGRAC).