The report said missed, incorrect or delayed diagnosis was the most common specific primary issue in complaints about services.
It was the primary reason for about 20 per cent of complaints.
Communication also featured prominently when complaints were analysed. Failure to communicate effectively was an issue in about 34 per cent of complaints.
The report said inadequate co-ordination of care was often noted in complaints. Patients often moved from one part of the health care system to another. It was essential different units communicated well and there was a safe and seamless system to ensure the patient received appropriate care at all stages, according to the report.