Title {1}	Intravenous immunoglobulin and intravenous methylprednisolone as optimal induction treatment in chronic inflammatory demyelinating polyradiculoneuropathy: protocol of an international, randomised, double-blind, placebo-controlled trial (OPTIC).
Trial registration {2a and 2b}.	ISRCTN registry (ISRCTN15893334), as of February 12th 2018
Protocol version {3}	V3.5.15MAY2020
Funding {4}	Princess Beatrix Spierfonds (Dutch Charity): grant ZonMW (Netherlands Organization for Health Research and Development for health related funding): grant GBS/CIDP Foundation International: grant GAIN UK: grant Sanquin Plasma Products (Dutch Blood Supply Foundation): logistical support
Author details {5a}	S.R.M. Bus1, L. Zambreanu2, A. Abbas3, Y.A. Rajabally3, R. Hadden4, R.J. de Haan5, C.A.J.M. de Borgie5, M.P. Lunn2, I.N. van Schaik1, 6, F. Eftimov1, on behalf of the OPTIC-study group. 1) Amsterdam UMC, University of Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam,the Netherlands; 2) National Hospital for Neurology and Neurosurgery, Centre for Neuromuscular Disease, London, United Kingdom; 3) University Hospitals of Birmingham, Regional Neuromuscular Service, Birmingham, United Kingdom; 4) King’s College Hospital, Department of Neurology, London, United Kingdom; 5) Amsterdam UMC, University of Amsterdam, Clinical Research Unit, Amsterdam, the Netherlands; 6) Spaarne Gasthuis, Haarlem, the Netherlands.
Name and contact information for the trial sponsor {5b}	Sponsor: Prof. B.M.J. Uitdehaag, MD, PhD, neurologist, Head of Department. Amsterdam UMC, University of Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam, the Netherlands. Telephone: (+ 31) 020 566 3942 Contact information coordinating principal investigator (PI): F. Eftimov, MD, PhD, neurologist. Amsterdam UMC, University of Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam, the Netherlands. Room H2-213. Meibergdreef 9, 1105 AZ. Amsterdam, the Netherlands. Telephone: (+31) 020 566 9111, Email: f.eftimov@amsterdamumc.nl
Role of sponsor {5c}	The sponsor played no role in grant applications, the design, data collection, trial management, data analysis and interpretation. These tasks were the responsibility of the steering committee (see below under 5d). University College London Hospitals (UCLH) are the delegated coordinator in the United Kingdom (UK). This manuscript was written by the authors ({5a}). This manuscript is based on protocol version 3.5.15MAY2020. Decision to submit this manuscript was made by the steering committee. Trial results will be published in an international peer-reviewed journal. The steering committee and writing committee will have full access to data after completion of the trial and will make the final decision to submit the manuscript. Funders have no role in study design, data collection and analysis, decision to publish, or preparation of future manuscript(s).