Validity, reliability and interpretability of the Thai version of the urticaria control test (UCT)

BACKGROUND The Long Form and Short Form of the German (original) version of the Urticaria Control Test (UCT) have shown to be valid and reliable instruments for assessing patients with all types of chronic urticaria (CU). The cutoff scores for identifying patients with well-controlled disease were  ≥  24 and  ≥  12 for Long and Short Forms, respectively. However, the sensitivity to change and minimal clinically important difference (MCID) of the UCT have never been systematically evaluated. This study aimed to investigate the validity, reliability, screening accuracy, sensitivity to change and MCID of the linguistically validated translation of the UCT into the Thai language for assessing CU in the Thai population. METHODS A structured translation and pre-testing were done to cross-culturally adapt the UCT for the Thai language. All measurement properties of both forms of the Thai UCT were validated in 169 patients with CU. RESULTS There were strong correlations between the Thai UCT score and disease activity, health-related quality of life impairment, and disease control (all correlations  ≥  0.7). Good internal consistency and excellent intra-rater reliability were demonstrated. The same cutoff scores to define patients with well-controlled disease should be used as those recommended for the original UCT version. MCIDs equated to increase in scores of 6 and 3 for the Long and Short Forms, respectively, of the Thai UCT should be used to identify patients who had minimal responses. Score increments of ≥ 10 and  ≥  6 for Long and Short Forms, respectively, should be used to define patients who had marked responses. CONCLUSIONS This study confirmed the applicability of the UCT for use in Thailand, a country that has a very different language and cultural setting than that of Germany and the United States. Further studies are required to examine the suitability of the UCT for use in the pediatric population.