The accuracy of surrogate decision makers: a systematic review

Clinicians currently rely on patient-designated and next-of-kin surrogates to make end-of-life treatment decisions for incapacitated patients. Surrogates are instructed to use the substituted judgment standard, which directs them to make the treatment decision that the patient would have made if he or she were capacitated. However, commentators have questioned the accuracy with which surrogates predict patients' treatment preferences.

A systematic literature search was conducted using PubMed, the Cochrane Library, and manuscript references, to identify published studies that provide empirical data on how accurately surrogates predict patients' treatment preferences and on the efficacy of commonly proposed methods to improve surrogate accuracy. Two of us (D.I.S. and D.W.) reviewed all articles and extracted data on the hypothetical scenarios used to assess surrogate accuracy and the percentage of agreement between patients and surrogates.

The search identified 16 eligible studies, involving 151 hypothetical scenarios and 2595 surrogate-patient pairs, which collectively analyzed 19 526 patient-surrogate paired responses. Overall, surrogates predicted patients' treatment preferences with 68% accuracy. Neither patient designation of surrogates nor prior discussion of patients' treatment preferences improved surrogates' predictive accuracy.

Patient-designated and next-of-kin surrogates incorrectly predict patients' end-of-life treatment preferences in one third of cases. These data undermine the claim that reliance on surrogates is justified by their ability to predict incapacitated patients' treatment preferences. Future studies should assess whether other mechanisms might predict patients' end-of-life treatment preferences more accurately. Also, they should assess whether reliance on patient-designated and next-of-kin surrogates offers patients and/or their families benefits that are independent of the accuracy of surrogates' decisions.