Not All Deaths in CKD Are from a Broken Heart

CKD is common, but outcomes remain poor, with a high incidence of death as eGFR declines.1 Two studies published in this issue of JASN examine the association between reduced kidney function and specific causes of death.2,3 Navaneethan et al.2 used electronic health records and a linked mortality registry from the state of Ohio in the United States to study adults with two eGFR values <60 ml/min per 1.73 m2. Thompson et al.3 used administrative health care data and linked laboratory information from the province of Alberta in Canada to study all adult deaths stratified by recent eGFR and urine protein results. Reliably ascertaining an individual’s cause of death is notoriously difficult, even in prospective cohort studies with central adjudication. In both of these retrospective analyses, administrative personnel recorded the cause of death in routine care using the International Classification of Diseases 10th Revision system. With this method of ascertainment, we expect that many deaths were classified incorrectly. Reasons for misclassification include scenarios with multiple causes of death, ill-defined causes of death, and a lack of autopsy data. Nonetheless, these studies by Navaneethan et al.2 and Thompson et al.3 provide several important messages for our consideration.