Use of bitot's spot in screening for Vitamin A deficiency in Nigerian children

Abstract

A total of 2,905 children between 6 and 71 months of age were selected using a 2 stage stratified sampling method and screened for xerophthalmia using World Health Organisation (WHO) criteria and vitamin a deficiency (VAD) using serum retinol < 20 µg/dl (low/marginal). Only 33 cases of xerophthalmia were seen representing a national prevalence of 1.1%. Only 8 children presented with Bitot's spots (XIB) representing 0.3% of the total number of children screened for marginal VAD and 24.2% of xerophthalmic cases. Corneal xerosis (stage X2) was the commonest (0.8%) ocular presentation amongst the total number of children screened and also amongst cases of xerophthalmia where it was responsible for 66.7%. 3 children with VAD (serum retinol < 10 µg/dl) presented with Bitot's spot, corneal xerosis and corneal scar respectively. All of these 3 children were severely malnourished and sick while one of them was moribund. No cases of conjunctival xerosis (X1A), corneal ulcer (X3A) or keratomalacia (X3B) were encountered in the study. Corneal scars (XS) attributable VAD was responsible to 0.1%. Stages X3A (corneal xerosis) and XS (corneal scars attributable toVAD) of xerophthalmia were above the WHO cutoff points. The national prevalence of marginal VAD defined as serum retinol was 28.1%. Despite its low prevalence, Bitot's spot can be a useful screening tool particularly in a field survey involving a large population of children because of the characteristic cluster distribution of VAD. The implication of this is that a single case of Bitot's spot points to a whole community at risk of VAD.