Objective: A new quality of life measure, a part of the National Health and Welfare 2003 survey, is a promising tool for outcome evaluation of clinical practice due to its brevity, validity, reliability, and providing easy interpretation against general population norm-based scores. The measure consisting of 9-items, and so called 9-item Thai Health status Assessment Instrument (9-THAI) was used to assess its validity and reliability in patients on renal replacement therapy (RRT).
Material and Method: Three hundred and two patients on RRT who visited Srinagarind Hospital from March to May 2005 were studied. Convergent and divergent validity were assessed using SF-36 as the concurrent measure. Concurrent validity was also assessed using hematocrit level and hospitalization history in the last year as concurrent clinical measures. Test-retest reliability was studied by repeated measure within one month. Responsiveness of 9-THAI was studied in patients who reported health improvement.
Results: Results of correlations between 9-THAI and SF-36 domains were as hypothesized. 9-THAI scores were significantly correlated with hematocrit level and hospitalization history. The results confirmed the validity of 9-THAI for use as a quality of life measure. Intraclass correlation coefficients of 9-THAI scores in stable patients were satisfactory. Among patients on RRT who reported overall health improvement, 9-THAI scores significantly increased, thus adding further evidence of the responsiveness of 9-THAI.
Conclusion: The 9-THAI is a valid and reliable generic health status measure that can be used as an ideal core in a battery of quality of life measures in clinical practice for patients on RRT.

Keywords: Health-related quality of life, Quality of life, Generic health status measure, Renal replacement therapy, SF-36, Validity, Reliability, Responsiveness