Generic outcome set for the international registry on Laser trEAtments in Dermatology (LEAD): a protocol for a Delphi study to achieve consensus on what to measure oleh Thierry Passeron, Murad Alam, Frederike Fransen, Phyllis Spuls, Ashraf Badawi, Pablo Boixeda, Merete Haedersdal, Iltefat Hamzavi, Lene Hedelund, Kristen M Kelly, Tara Kono, Hans Joachim Laubach, Woraphong Manuskiatti, Leonardo Marini, Keyvan Nouri, Uwe Paasch, Cecilia A.C. (Sanna) Prinsen, Ines Verner, Albert Wolkerstorfer