Vitamin A deficiency among children in a periurban South African settlement

Physiologic indicators of vitamin A status

Physiologic indicators reflect the functional consequences of vitamin A deficiency and may be particularly useful for detecting early perturbations in vitamin A status. In conjunctival impression cytology (CIC), epithelial morphology and the presence or absence of mucin spots and goblet cells allow samples, obtained by applying filter paper to the temporal conjunctiva, to be characterized as normal or typical of vitamin A-deficient keratinizing metaplasia. The validity of CIC has been established with reference to other indicators of vitamin A status, and a prevalence of > or =20% abnormal results has been suggested as indicative of a public health problem. However, interpretation of specimens requires considerable training, and nonresponsiveness to supplementation is a frequent problem, which limits the utility of CIC as a method for evaluating the impact of intervention programs. Several simplified field protocols for dark adaptation have been developed, including one in which dark adaptation is assessed by the responsiveness of the pupil to light. Night blind subjects have consistently shown abnormal results on this test, and a significant response to placebo-controlled dosing has been demonstrated for children and pregnant women. Scores have correlated significantly with serum retinol and relative dose response. Pupillary dark adaptation testing is acceptable to most children as young as 2 y old. Limitations of this technique include a time course for recovery after dosing as long as 4-6 wk, a testing time of 20 min, and the need for 1-3 d of training. Given its low cost, noninvasive nature, and lack of the need to transport samples, pupillary dark adaptation offers advantages over other techniques for assessing a population's vitamin A status.

Urbanisation and vitamin A deficiency in children: comparison between a traditional district and a new settlement in Mali

OBJECTIVES

The purpose of this study was to assess the vitamin A status of pre-school urban children and to compare the situation between a traditional district and a new settlement after two decades of intense urbanisation.

SUBJECTS AND METHODS

A cross-sectional stratified survey was carried out in Bamako, Mali, on a representative sample of children (aged 4-6 years). 532 children were involved from a traditional district and 453 from a new settlement (NS). The vitamin A status was assessed by: clinical indicators (ophthalmic examination), subclinical indicators (questionnaire looking for night blindness, impression cytology with transfer test (ICT), modified relative dose response test (MRDR), and a diet inquiry about vitamin A intakes. Acute malnutrition was assessed by a weight/height measure.

RESULTS

In both districts, all the clinical indicators were below the WHO criteria that define a public health problem. Both the ICT test, respectively 19 and 21% of abnormal tests, and the MRDR, 67.3 and 73.1% of tests > or = 0.06, indicated a subclinical vitamin A deficiency as defined by WHO thresholds. During the preceding week only four children in NS had consumed vitamin A-rich food less than seven times. No significant difference between the two districts was found either for clinical or subclinical indicators (p > 0.5).

CONCLUSION

Despite a rapid urbanisation, the vitamin A status of the children seemed to be rather homogeneous among the different districts. The population remained vulnerable with peripheral depletion and low hepatic stores of vitamin A. The urban children should be carefully monitored regarding vitamin A status.