Ponjoan A, et al. - Given the emergence of electronic health records from primary care in Alzheimer’s disease (AD) research, researchers sought to determine their accuracy via verifying AD diagnoses from primary care using additional information provided by general practitioners (GPs), and a register of dementias. In the System for the Development of Research in Primary Care (SIDIAP), AD cases were identified combining International Statistical Classification of Diseases (ICD-10) and Anatomical Therapeutic Chemical codes with three algorithms. Dementia diagnoses were evaluated by GPs by means of an online survey. In addition, data from the Register of Dementias of Girona and from SIDIAP were linked. Findings revealed differences in positive predictive value (PPV) estimates depending on the gold standard. Improvement in the AD case ascertainment was achieved with the development of algorithms integrating diagnoses and treatment of dementia. Given high PPV and sensitivity estimates, AD codes recorded in a large primary care database seem to be adequately reliable for research purposes.