Minimal clinically important difference for acupuncture for patients with chronic spontaneous urticaria: secondary analysis from a multicentre randomised controlled trial in China

Objectives: To evaluate the minimal clinically important difference (MCID) value for acupuncture treatment in chronic spontaneous urticaria (CSU), providing guidance for its application in CSU management.

Design: Secondary analysis of data from a multicentre randomised controlled trial.

Setting: Three tertiary hospitals across three cities in China.

Participants: 103 CSU patients (78.7% female) with an average age of 39.97 years.

Interventions: Participants received acupuncture treatment for 4 weeks in the original study.

Outcome measures: MCID and minimal detectable change (MDC) for the Urticaria Activity Score over 7 days (UAS7) in acupuncture treatment of CSU. Convergent validity assessed by intraclass correlation coefficient (ICC). Responsiveness evaluated through Spearman correlation between UAS7 improvements and anchor tools (physician's and patient's assessments). MDC calculated using SE of measurement of changes in UAS7 scores. MCID estimated using distribution-based and anchor-based methods.

Results: The ICC for UAS7 was 0.86. Improvements in UAS7 scores were significantly correlated with patient (r=0.44, p<0.01) and physician (r=0.85, p<0.01) assessments of CSU activity shifts. The MDC for UAS7 was 5.08. The MCID for acupuncture treatment in CSU was 8.3.

Conclusions: This study provides the first MCID value for acupuncture treatment in CSU. These findings contribute to the understanding of acupuncture's effects in treating CSU and may inform future research and clinical practice in the management of this condition.

Trial registration number: ChiCTR1900022994.