%C United States %D 2018 %T Classification of death causes after transplantation (CLASS): Evaluation of methodology and initial results %K cancer, infection, methodology, transplantation death causes classification %N 29 %V 97 %L discovery10053562 %J Medicine %A NE Wareham %A C Da Cunha-Bang %A ÃH Borges %A C Ekenberg %A J Gerstoft %A F Gustafsson %A D Hansen %A C Heilmann %A M Helleberg %A J Hillingsø %A PS Krohn %A IP Lodding %A TK Lund %A L Lundgren %A A Mocroft %A M Perch %A SL Petersen %A I Petruskevicius %A A Rasmussen %A K Rossing %A AA Rostved %A H Sengeløv %A VR Sørensen %A SS Sørensen %A JD Lundgren %O Copyright © 2018 the Author(s).This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CC BY-NC-ND) (http://creativecommons.org/licenses/by-nc-nd/4.0), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. %X Correct classification of death causes is an important component of transplant trials.We aimed to develop and validate a system to classify causes of death in hematopoietic stem cell (HSCT) and solid organ (SOT) transplant recipients.Case record forms (CRF) of fatal cases were completed, including investigator-designated cause of death. Deaths occurring in 2010 to 2013 were used for derivation; and were validated by deaths occurring in 2013 to 2015. Underlying cause of death (referred to as recorded underlying cause) was determined through a central adjudication process involving 2 external reviewers, and subsequently compared with the Danish National Death Cause Registry.Three hundred eighty-eight recipients died 2010 to 2015 (196 [51%] SOT and 192 [49%] HSCT). The main recorded underlying causes of death among SOT and HSCT were classified as cancer (20%, 48%), graft rejection/failure/graft-versus-host-disease (35%, 28%), and infections (20%, 11%). Kappa between the investigator-designated and the recorded underlying cause of death was 0.74 (95% CI 0.69-0.80) in derivation and comparable in the validation cohort. Death causes were concordant with the Danish National Death Cause Registry in 37.2% (95% CI 31.5-42.9) and 38.4% (95% CI 28.8-48.0) in the derivation and validation cohorts, respectively.We developed and validated a method to systematically and reliably classify the underlying cause of death among transplant recipients. There was a high degree of discordance between this classification and that in the Danish National Death Cause Registry.