The study referred to by Houlind et al1 demonstrates that an abnormally low eGFRcystatin C:eGFRcreatinine ratio in hospitalized older Danish adults is associated not only with lower kidney function, but also with higher rates of malnutrition and greater established comorbidity. This agrees with the greater morbidity previously noted in several studies of patients with a low eGFRcystatin C:eGFRcreatinine ratio,2 which might contribute to the strong increase in mortality also noted in such patients.