This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/dta.2555 This article is protected by copyright. All rights reserved. TITLE Hair analysis to discriminate voluntary doping vs inadvertent ingestion of the aromatase inhibitor letrozole SHORT TITLE Letrozole incorporation in hair samples Authors: Donata Favretto 1,2 , Rossella Snenghi 1 , Roberto Pertile 1 , Rafi El Mazloum 2 , Marianna Tucci 2 , Sindi Visentin 1,2 *, Susanna Vogliardi 2 1 University Hospital of Padova, Via Falloppio 50, 35121, Padova, Italy 2 Department of Cardiac Thoracic and Vascular Sciences and Public Health, University of Padova, Padova, Italy Address correspondence to: Dr. Sindi Visentin e-mail: sindi.visentin@gmail.com Address: Department of Cardiac Thoracic and Vascular Sciences and Public Health, University of Padova, Padova, Italy Funding Source: no funding source. Disclosure statement: The authors have no financial relationships relevant to this article to disclose. Conflict of Interest: None