Competing interests CRJ serves on scientific advisory boards for Elan Corporation/Janssen Alzheimer Immunotherapy (Dublin, Ireland), Eli Lilly and Company (Indianapolis, IN, USA), GE Healthcare (Little Chalfont, Buckinghamshire, UK), and Eisai Inc. (Woodcliff Lake, NJ, USA); receives research support from Baxter International quality control Inc. (Deerfield, IL, USA), Allon Therapeutics Inc. (Vancouver, BC, Canada), and Pfizer Inc (New York, NY, USA); and holds stock/stock options in Johnson & Johnson (New Brunswick, NJ, USA). PV and DTJ declare that they have no competing interests. Acknowledgements PV receives support from National Institute on Aging grant K99 AG37573 (as principal investigator) and an Alzheimer’s Association New Investigator Research Grant.

CRJ receives support from National Institute on Aging grants R01 AG11378 (as principal investigator), P50-AG16574 (as co-investigator), and U01 AG024904-01 (as co-investigator) and the Alexander Family Alzheimer’s Disease Research Professorship of the Mayo Foundation.

Patient-reported outcome (PRO) measures are used to evaluate the impact of disease and treatment in many therapeutic areas. Among the advantages of patient report is the potential to capture aspects of the disease and treatment experience uniquely accessible to patients and, relatedly, to improve the measurement of therapeutic intervention effects [1]. The clinician’s specialized framework of knowledge makes the clinician the most accurate reporter for some aspects of the disease experience.

For which is the patient the more accurate reporter? The most recent recommendations for core clinical criteria for the diagnosis of mild cognitive impairment (MCI) due to Alzheimer’s disease (AD) [2] note that despite ‘preservation of independence in functional abilities’ some impairment in complex functional tasks may be evident, such as higher error rate, taking longer, and/or being less efficient. The companion statement on research criteria for preclinical stages of AD [3] raises the possibility that biomarkers in combination with ‘subjective assessment of subtle change will prove to be useful.’ Subtle but potentially important features of the disease experience may be inaccessible to those other than the patient, raising the interesting possibility that the patient may have the most comprehensive and accurate knowledge of performance [4].

Although impairment in social or occupational functioning Anacetrapib is part of AD diagnostic criteria [5], the place of functioning in diagnostic definitions of MCI is still evolving [2,6-8]. Initial definitions of MCI were based on cognitive impairment and intact activities of daily living [9], but empirical data support the presence of functional deficits encompassing skills and activities beyond instrumental activities of daily living (ADLs), many of them subtle [10-15]. Functioning therefore emerges as an area of potential value kinase inhibitor Tubacin for patient self-report.