The development and initial validation of the Liverpool sicca index to assess symptoms and dysfunction in patients with primary Sjögren's syndrome

Background:  A validated measure to assess sicca-related symptoms in patients with primary Sjögren's syndrome (1°SS) is required for clinical studies. Methods:  A self-administered questionnaire was developed to assess sicca-related symptoms and dysfunction in 1°SS. This was administered to three groups of 40 respondents to measure construct validity: 1°SS patients, non-SS patients reporting xerostomia and a non-patient group. The frequency of scores and the mean score for each question were calculated for each group. Reliability was assessed by test/retest. Results:  The measure consisted of 28 items divided into five domains. Scores for questions in domains were generally worse (higher) for 1°SS patients than for patients with xerostomia. The non-patient group reported the best (lowest) scores for all questions. The Kappa statistic for all but four questions was greater than 0.6, suggesting good reliability. Conclusion:  Questionnaire showed good construct validity and reliability. The Liverpool sicca index needs to be further validated in larger, multicentre studies.