Application of the Itch Severity Score in patients with moderate-to-severe plaque psoriasis: Clinically important difference and responder analyses

Abstract

The Itch Severity Score (ISS), a 0–10 numeric rating scale, was used to assess pruritus due to psoriasis in a Phase 2 b trial of tofacitinib, a novel oral Janus kinase inhibitor. 197 patients with moderate-to-severe plaque psoriasis were randomized to tofacitinib 2, 5 or 15 mg twice daily, or placebo. The ISS was recorded daily from baseline to week 2 and at study visits. Following good and recommended research practice, we performed analyses to examine the clinically important differences (CID) (between-group difference or within-group difference) and clinically important responders (CIR) (within-patient change) for the ISS. The CID and CIR were defined using Patient Global Assessment of psoriasis as an anchor and were estimated with a longitudinal model. A CID on the ISS was 1.64 and, by day 10, the mean changes from baseline in ISS values for the tofacitinib doses (placebo-adjusted) exceeded CID. A CIR on the ISS was a 30% improvement from baseline and, at week 12, 87.2% to 100% of patients receiving tofacitinib reached ≥30% improvement versus 29.4% of patients receiving placebo (p < 0.0001). Overall, the CID and CIR analyses play vital roles in the interpretation of the treatment effects measured by ISS.

• Clinically important difference
• clinically important responders
• ISS
• pruritus
• psoriasis
• tofacitinib

Acknowledgements

The authors would like to thank the Study A3921047 investigators, patients and study team.

Investigators

Canada: Dr Robert Bissonnette, Dr Marc Bourcier, Dr Jerry K.L. Tan, Dr Yves Poulin, Dr Kim Papp, Dr Wayne D. Carey, Dr Wayne P. Gulliver, Dr Aditya K. Gupta, Dr Vincent Ho, Dr Rodion A. Kunynetz, Dr Richard Langley, Dr Catherine H. Maari, Dr Leslie Rosoph, Dr Darryl Toth

USA: Dr Jerry Bagel, Dr Diane R. Baker, Dr Alicia R. Barba, Dr Charles A. Birbara, Dr Marie F. Bruyneel, Dr Lesly S. Davidson, Dr Jonathan S. Dosik, Dr Frank E. Dunlap, Dr Joel M. Gelfand, Dr Paul Getz, Dr Paul S. Gillum, Dr Alice B. Gottlieb, Dr John M. Humeniuk, Dr Jonathan Kantor, Dr Alexandra B. Kimball, Dr Neil J. Korman, Dr Gerald G. Krueger, Dr Patricia C. Lee, Dr Craig L. Leonardi, Dr Robert T. Matheson, Dr Martin A. Menter, Dr David M. Pariser, Dr Phoebe P. Rich, Dr Patricia N. Speelman, Dr David M. Spencer, Dr Bruce E. Strober, Dr John H. Tu, Dr Stephen K. Tyring

Declaration of interest

All authors are employees of Pfizer Inc and hold stock/stock options in Pfizer Inc. This research was sponsored by Pfizer Inc. Medical writing support was provided by Karen Irving of Complete Medical Communications, and was funded by Pfizer Inc.

Notes

* Prior publication/presentation: The contents of this manuscript have not been previously published and are not currently submitted elsewhere. The study was presented as a poster at the International Society for Pharmacoeconomics and Outcomes Research 16th Annual International Meeting, Baltimore, MD, USA, 21–25 May 2011, and at the American Academy of Dermatology 69th Annual Meeting, New Orleans, LA, USA, 4–8 February 2011.