Analysis of the correlations of mucins, inflammatory markers, and clinical tests in dry eye.

Purpose: To investigate the expression of mucin and inflammatory factors in the conjunctival epithelium of subjects with dry eye and determine a correlation between clinical laboratory tests and subjective symptoms.
Methods: The ocular surface disease index questionnaire, corneal fluorescein staining, tear film breakup time, and Schirmer I tests were administered in 66 subjects. According to questionnaire scores, the subjects were divided into mild, moderate, and severe symptom groups. Then, the subjects were divided based on the clinical tests into negative and positive groups. Impression cytology specimens from all patients were immunolabeled with antibodies directed against human mucin 5AC (MUC5AC) and interleukin-6 (IL-6) and the staining density was measured.
Results: MUC5AC was lower in the severe symptom group compared with the mild and moderate symptom groups (P < 0.001, respectively). IL-6 was higher in the severe symptom group compared with the mild and moderate symptom groups (P < 0.001, respectively), and also in the moderate symptom group compared with the mild symptom group (P < 0.001). A decrease of MUC5AC was found in the positive group compared with the negative group (P < 0.001). IL-6 was higher in the positive group compared with the negative group (P = 0.029). MUC5AC was negatively correlated with the ocular surface disease index scores (r = -0.697, P < 0.001), whereas IL-6 positively correlated the scores (r = 0.895, P < 0.001). There were weak correlations for MUC5AC and IL-6 with tear film breakup time (r = 0.158 and r = -0.195, respectively; P = 0.038 and P = 0.041, respectively), and no correlations with other clinical tests.
Conclusions: Dry eye disease is associated with decreased levels of mucin and an overexpression of IL-6, which correlate to the symptomatic severity of disease.