Conjunctival impression cytology for assessment of vitamin A status.

Ocular signs and serum vitamin A concentrations are commonly used for the diagnosis of vitamin A deficiency. Recently, impression cytology was suggested as a method for early detection of this condition. A clinical trial was conducted to compare the results of impression cytology with the other two indicators of vitamin A status. A total of 246 children aged 1-10 y were investigated. About 25% of the children with normal eyes showed abnormal cytology. Their mean vitamin A concentrations were significantly lower compared with those with normal cytology, which suggests that abnormal cytology reflects subclinical deficiency. After treatment with vitamin A, most of the children who had abnormal cytology at baseline examination showed improvement. These observations suggest that abnormal cytology is specific to vitamin A deficiency. Impression cytology is a relatively simple technique and can be used for assessing the magnitude of the problem, especially in communities where the prevalence of clinical disease is low.