BackgroundCommunication between involved parties is essential to ensure coordinated and safe health care delivery. However, existing literature reveals that the information relayed in the referral process is seen as insufficient by the receivers. It is unknown how this insufficiency affects the quality of care, and valid performance measures to explore it are lacking. The aim of the present study was to develop quality indicators to detect the impact that the quality of referral letters from primary care to specialised mental health care has on the quality of mental health services.MethodsUsing a modified version of the RAND/UCLA appropriateness method, a systematic literature review and focus group interviews were conducted to define quality indicators for mental health care expected to be affected by the quality of referral information. Focus group participants included psychiatrists, psychologists, general practitioners, patient representatives and managers. The existing evidence and suggested indicators were presented to expert panels, who assessed the indicators by their validity, reliability, sensitivity and feasibility.ResultsSixteen preliminary indicators emerged during the focus group interviews and literature review. The expert panels recommended four of the 16 indicators. The recommended indicators measure a) timely access, b) delay in the process of assessing the referral, c) delay in the onset of care and d) the appropriateness of the referral. Adjustment was necessary for five other indicators, and seven indicators were rejected because of expected confounding factors reducing their validity and sensitivity.ConclusionsThe quality of information relayed in the referral process from primary care to specialised mental health care is expected to affect a wide range of dimensions defining high quality care. The expected importance of the referral process for ensuring ‘timely access’-one of the six aims of high-quality health care defined by the Institute of Medicine-is highlighted. Exploring the underlying mechanisms for the potential impact of referral information on patient outcomes is recommended to enhance quality of care.Trial registrationClinicalTrials.gov: NCT01374035 (28 April 2011).