Relationship of conjunctival impression cytology with clinical and biochemical assessment of vitamin A status of preschoolers

Comparison of conjunctival impression cytology (CIC) with ocular signs and vitamin A levels was done based upon a national nutrition survey involving 427 randomly selected subjects aged 6 months to 6 years. Medical nutritionists looked for ocular signs and performed conjunctival impressions. Imprints were submitted to the Institute of Ophthalmology, University of the Philippines-Philippines General Hospital, for analysis. Fixing, staining and reading of all imprints was performed in accordance with the procedures of the International Centre for Epidemiologic and Preventive Ophthalmology (ICEPO). Comparison of the biochemical determination of serum vitamin A (SVA) with CIC results revealed that irrespective of SVA levels, more than 50% of the subjects were noted to have abnormal CIC results. The highest proportion of abnormal imprints was seen among those with low SVA. The relationship, however, was found not to be significant. Of the 247 subjects examined, 95% had a normal clinical and biochemical assessment of vitamin A; of these, 50.2% had abnormal cytology imprints while 45.3% had normal imprints. Using sensitivity and specificity analyses, CIC was compared with SVA levels. The computed sensitivity, specificity and positive predictive value (PPV) were 60.5, 45.2 and 60.0%, respectively. The lack of significant difference in mean serum retinol levels between normal and abnormal CIC groups may partly explain the low sensitivity and PPV of the CIC. In this study population, CIC failed to identify children with subclinical vitamin A deficiency as established by biochemical examination.