DISCUSSION
Our study is the first to validate the use of the UCT in the evaluation of pediatric CU. We demonstrated that the UCT has adequate internal consistency, convergent validity, known-groups validity, and screening accuracy when compared to the CDLQI at study entry and at follow-up. Similar results were observed in subgroup analyses of CSU and CIndU patients, although we were unable to assess the convergent validity of the UCT in CIndU cases because of inadequate sample size. Furthermore, a greater increase in UCT scores was observed in patients who started or increased their dose of sgAHs, which exemplifies the clinical relevance of the UCT.
Results of the validation of the UCT in adult CU were largely consistent with our study. Internal consistency of the UCT in adult CU was excellent (Cronbach’s α=0.84)14, whereas our results revealed respectable internal consistency in pediatric CU (Cronbach’s α=0.73). Validation of the Turkish UCT revealed lower internal consistency of the UCT in CIndU compared to CSU (0.89 versus 0.68, respectively), whereas values were similar in our results17. Although DLQI and CDLQI scores are not directly comparable24, in adult CU, UCT scores strongly negatively correlate with DLQI scores (Spearman’s rho=-0.72)25. Consistent with our results in children, the UCT can distinguish between known-groups of disease severity in adults17,26. Screening accuracy (i.e., AUC) of the UCT in adult CU was also excellent, although slightly higher than in our findings (0.89 versus 0.82, respectively)14. We found a slightly lower optimal cut-off for poorly controlled CU in children (UCT≤10) than was determined for adults (UCT≤11)14. A cut-off of 10 in children had a poorer specificity (63.3% versus 70.8%) but greater sensitivity (95.5% versus 89.9%) than a cut-off of 11 in adults14. The discrepancy between the cut-off of poorly controlled CU in adults and children may be because no studies exist formally validating a CDLQI cut-off for poorly controlled CU. Despite using a previously published CDLQI cut-off21, misclassification bias may persist.
No tools exist to evaluate CU symptom control and severity in children, thereby limiting the evaluation of outcomes, progression, and management in pediatric CU trials5,13. Patient reported outcome tools, like the UCT, have been recommended as endpoints in clinical trials27 and in the assessment of adult CU15. Although the UAS7 has not been specifically validated in pediatric CSU, current pediatric guidelines suggest that it may be used in the evaluation of pediatric CSU3,5. However, the UAS7 has several limitations compared to the UCT. Firstly, the UAS7 is only designed to assess CSU and not CIndU28. Secondly, the UAS7 must be completed prospectively, which poses logistical and compliance challenges. Thirdly, the UAS7 does not evaluate angioedema or disease control. Therefore, the retrospective nature of the UCT, the ability to assess CIndU, and the evaluation of angioedema and disease control strongly favours the use of the UCT in the evaluation of pediatric CU and in future clinical trials14.
Our study is subject to some limitations. The low sample size precluded the evaluation of the test-retest probability of the UCT. Therefore, we recommend future multi-center studies validating the use of the UCT in children. The recall periods of the UCT and the CDLQI are not the same (28 versus 7 days, respectively). Therefore, it is possible that acute exacerbations of CU were captured by the UCT and not the CDLQI. This discrepancy could reduce the convergent validity and the known-groups validity of the UCT and may lead to the misclassification of patients in the assessment of screening accuracy. Although the CDLQI is only validated in children aged 4 to 16 years8, our study included children of any age, which may bias the results. However, subgroup analysis of only patients aged 4 to 16 years yielded largely consistent results with the entire sample. Furthermore, the CLDQI is not a CU-specific tool; therefore, concomitant dermatologic diseases (i.e., atopic dermatitis) may have elevated the CDLQI scores, which would not have been detected by the UCT. Despite the flaws of the CLDQI, it is the only validated questionnaire that can be used in pediatric CU.
In conclusion, our findings validate the use of the UCT as a patient reported outcome in the assessment of pediatric CU and CSU. Larger studies are necessary to validate the convergent validity of the UCT in pediatric CIndU.