Published online: November 8, 2017
Chronic spontaneous urticaria (CSU) is a prevalent disease, with a point prevalence of up to 1% of the general population. It is characterized by the recurrent formation of transient itchy hives for longer than six weeks. Individual hives usually persist for less than 24 hours. Urticaria symptoms usually fluctuate considerably from day to day. As of now, no biomarker exists to reliably determine disease activity in CSU. Therefore, urticaria activity can only be evaluated by the use of patient reported outcome (PRO) measures. The urticaria activity score (UAS), used for seven consecutive days (UAS7), is an established and widely accepted PRO tool to prospectively assess CSU activity. The UAS7 has been widely used in recent years in clinical practice and in most clinical trials in CSU as a main outcome parameter. The UAS entails the assessment of the two key urticaria signs and symptoms: wheals and itch. Two versions of this tool exist. They differ in two aspects: 1) Their categories of wheal numbers are different, 2) their mode of documentation, i.e. once daily for the UAS7 and twice daily for the UAS7TD. Both tools have the same total score, which ranges from 0 (no disease activity) to 42 (maximal disease activity). The international EAACI/GA2LEN/EDF/WAO guideline for urticaria recommends using the once daily UAS7. Its use is less burdensome for patients and easier for evaluation by physicians, than that of the twice-daily version. Some critical clinimetric data of the UAS7 are still missing.
In a recent issue of The Journal of Allergy and Clinical Immunology: In Practice, Hawro and colleagues present parameters of validity, reliability, sensitivity to change, minimal important difference (MID), and smallest detectable change (SDC) for the UAS7 and the UAS7TD. 130 patients with difficult-to-treat CSU, before the initiation of therapy with omalizumab, were recruited to the study. During the two weeks before omalizumab therapy and the four weeks thereafter, patients were asked to prospectively document their disease activity by using both, the UAS7 and the UAS7TD along with the Patients’ Global Assessment (PatGA) and other validated PROs such as the Urticaria Control Test (UCT), the Chronic Urticaria Quality of Life Questionnaire (CU-Q2oL), and the Dermatology Life Quality Index (DLQI). Physicians documented the Physicians’ Global Assessment (PhyGA).
Both instruments, the UAS7 and the UAS7TD, were found to exhibit good convergent validity, i.e. their results correlated well with those of the applied anchor instruments for disease activity, disease control, and health-related quality of life impairment. Both UAS7 instruments showed respectable internal consistency (Cronbach α coefficients of the UAS7 and the UAS7TD were 0.78 and 0.77, respectively), excellent test-retest reliability (intraclass correlation coefficients for the UAS7 and the UAS7TD were 0.83 and 0.86, respectively), and they were sensitive to change in disease activity. The minimal important difference (MID), i.e. the difference in the instrument score that is not only statistically significant but also clinically relevant for patients in real life, was 11 points for the UAS7 and 12 points for the UAS7TD.
This study provides, for the first time, clinimetric data for the UAS7, and it confirms and extends the previous US clinimetric data for the UAS7TD. The results prove that both available variants of the UAS are appropriate and valid tools to measure disease activity in patients with CSU. In addition, the study provides important information for the interpretation of UAS score changes. Since the clinimetric properties of both UAS versions are comparable, the authors suggest that the use of the once daily UAS7 should be preferred as it is less burdensome in administration and scoring.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.