How well do blood folate concentrations predict dietary folate intakes in a sample of Canadian lactating women exposed to high levels of folate? An observational study

Table 3 Percentage of participants correctly, closely or misclassified into quartiles of folate intake compared with classification by blood folate indexes

Variable	n	Correctly Classified	Closely Classified¹	Misclassified²	P value³
4 wks postpartum
Supplement users + nonusers
Plasma folate	53	28	44	28	0.1427
RBC folate	53	40	40	20	< 0.001
Unsupplemented
Plasma folate	17	18	41	41	0.2707
RBC folate	17	35	30	35	0.0588
16 wks postpartum
Supplement users + nonusers
Plasma folate	55	47	33	20	<0.0001
RBC folate	55	33	43	24	< 0.05
Unsupplemented
Plasma folate	18	6	50	44	<0.0001
RBC folate	18	22	39	39	0.7866

¹ Percentage of participants misclassified by one quartile
² Percentage of participants misclassified by two or more quartiles
³ A P-value < 0.05 indicates a rejection of the null hypothesis that there is no association between folate intakes and blood folate concentration based on the expectation that 25% of participants would be correctly classified, 37.5% closely classified and 37.5% misclassified. The actual numbers are compared with expected numbers using chi-square goodness of fit with 2 df.

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