Diagnostic value of contrast sensitivity test and conjunctival impression cytology for the detection of sub-clinical vitamin-a deficiency
Purpose: To determine whether or not contrast sensitivity test and conjunctival impression cytology can be used as diagnostic tools to detect sub-clinical vitamin-A deficiency; and if there is a correlation within the two diagnostic methods.
Methods: A series of diagnostic studies comprising of contrast sensitivity test, conjunctival impression examination and serum retinol concentration were performed on literate children, six to ten years old, at West Java Elementary School. All subjects underwent a basic eye examination. Sample size, receiver operator curve, negative and positive predictive values, sensitivity and specificity were calculated.
Results: A total of 109 subjects out of 154 elementary school children corresponding to the inclusion criteria were included in this study. Forty-four (41.9%) children were detected to have sub-clinical vitamin-A deficiency. The contrast sensitivity test had a sensitivity value of 45.5% and a specificity value of 50.8% with a positive predictive value of 40%. The area under the receiver operator characteristic (ROC) curve was 49.5% (95% CI 38.1%- 60.9%), whereas the conjunctival impression cytology test had a sensitivity value of 90.9%, and a specificity value of 16.4% with a positive predictive value of 43.9%. The ROC area was 56.1% (95% CI 45.0% - 67.1%). Pearson’s analysis showed that there is no correlation between the two diagnostic tools (p 0.538).
Conclusion: The results of this study indicated that neither the contrast sensitivity test nor the conjunctival impression cytology was found to be a favorable screening tool to detect sub-clinical vitamin-A deficiency. Moreover, there is no correlation between the two methods.