Conjunctival impression cytology and biochemical assessment of vitamin A status in Nigerian children.

The study was part of a national survey designed as cross-sectional population survey to estimate the prevalence of Vitamin A deficiency in Nigeria. A multistage cluster random sampling technique was used to select about 163 children between 6 and 71 months of age in 2 health zones of Nigeria, for assessment of their vitamin A status. Conjunctival Impression Cytology (CIC) was compared with biochemical method by estimating serum level of vitamin A using the reverse phase high pressure liquid chromatography (HPLC). Conjunctival impressions were taken from both temporal bulbar conjunctivae of 483 children using the disc applicator. CIC showed significant association with low serum retinol (0.70 umol/l) levels. Children with abnormal CIC had 2.6 times the risk of having low serum retinol levels compared with those with normal CIC (OR = 2.6, 95% C.I = 1.03-6.67). When CIC was classified as normal and abnormal at cut off points of retinol at 0.70 and 0.35 umol/l, the sensitivity of CIC remained low, while the specificity remained high. Although our study did not demonstrate valuable use of CIC as a screening tool under field conditions in a tropical environment like Nigeria, our impression is that, if the technique is further refined and evaluated, there is a high potential for its use in developing countries, because of its simplicity, practicability and non-invasiveness.