Maternal vitamin levels during pregnancies producing infants with neural tube defects.

Women at very high risk for having a child with a neural tube defect (NTD) because they had previously delivered affected children significantly reduced their recurrence rate by taking folate supplements before conception. To clarify how these results might apply to a lower-risk general obstetric population, we measured folate, vitamin B12, and retinol levels in maternal serum drawn early in 89 pregnancies resulting in NTD offspring and 178 control pregnancies identified from the Finnish Registry of Congenital Malformations. In 86.5% of the subjects, specimens were collected within 8 weeks after neural tube closure. In the NTD case mothers the mean (+/- SD) levels were not significantly lower than in control mothers: folate, 4.13 +/- 2.36 versus 4.28 +/- 2.52 ng/ml; vitamin B12, 482.8 +/- 161.1 versus 520.3 +/- 191.9 pg/ml; and retinol, 51.2 +/- 17.0 versus 50.5 +/- 16.9 micrograms/dl. After adjustment for age of the specimen, gestational age at which the specimen was drawn, maternal age, and maternal employment status, the odds ratios for being a case mother were 1.00 (95% confidence interval (CI) 0.91 to 1.10) for folate, 1.05 (95% CI 0.92 to 1.19) for vitamin B12, and 0.99 (95% CI 0.88 to 1.10) for retinol. Excluding NTD cases with known or suspected causes unrelated to vitamins, restricting the analyses to interviewed subjects, and excluding subjects whose specimens were collected after 15 gestational weeks confirmed that NTD case and control vitamin levels did not differ significantly. This population-based investigation in a low rate area demonstrated no relationship between maternal serum folate, vitamin B12, or retinol levels during pregnancy and the risk of NTDs.

Conjunctival impression cytology: feasibility of a field trial to detect subclinical vitamin A deficiency.

Two hundred and thirty-six Guatemalan children aged 2-14 y were examined for subclinical vitamin A deficiency by use of conjunctival impression cytology (CIC). The feasibility of the technique and quality of a modified touch procedure were assessed. Neither lid speculum nor physical restraint in the form of a papoose board was used. The CIC technique was easily performed on children aged greater than 3 y but was more difficult among those less than or equal to 3 y. Laboratory processing of specimens is uncomplicated but interpretation may be problematic and requires clearly defined criteria of normal and abnormal cytology as well as careful standardization of readers.

Conjunctival impression cytology (CIC) to detect subclinical vitamin A deficiency: comparison of CIC with biochemical assessments.

By use of sensitivity and specificity analysis, conjunctival impression cytology (CIC) was compared with fasting serum vitamin A levels and relative dose response (RDR) of Guatemalan children. One impression was taken from the temporal bulbar aspect of each eye, fasting serum vitamin A levels were then drawn, 480 RE of oil-based retinyl palmitate was given, and a 5-h postdosing vitamin A level was drawn (RDR procedure). For a 20% RDR cutoff, the sensitivity of CIC was 23% with a specificity of 80% and a positive predictive value of 9% (n = 213 children). Compared with fasting vitamin A levels alone (with 0.70 mumol/L as abnormal), the sensitivity of CIC was 26%, specificity was 81%, and positive predictive value was 22% (n = 221 children). There was no significant difference in the mean serum retinol level between those with abnormal and normal CIC. In this study population CIC does not identify the same group of children with marginal vitamin A as identified biochemically.