Hagberg KW, et al. - This study aims to calculate the positive predictive value (PPV) of autism spectrum disorder (ASD) diagnoses recorded in the Clinical Practice Research Datalink (CPRD) compared to original medical records and to describe characteristics of cases and use of clinical codes that support the ASD diagnosis as recorded in the electronic data by general practitioners over time. The authors reveal that in the CPRD, ASD diagnoses recorded are reliable and can be used with confidence to study ASD.