Table 1 Short descriptions of the operationalization of the different types of low-value GP care, including from which guidelines they were derived (additional file 1 contains an elaborate description of the specific diagnose codes included):

1. The use of imaging in the diagnosis of musculoskeletal complaints related to the back or knee. Dutch GP guidelines do not recommend to order imaging in case of non-specific knee or back pain. For our assessment we selected all episodes related to back or knee pain were selected. Next, all contacts with a code indicating they resulted in an imaging procedure were matched to each episode based on their unique episode identifier. The episodes with an associated contact indicating the performance of an imaging procedure were considered to have received low-value imaging [28,29,30]

2. The prescription of antibiotics for otitis media acuta (OMA) in children without severe symptoms. Guidelines recommend not to prescribe antibiotics in case of otitis media in children without the patient being seriously ill or without them being at risk of complications. For our assessment, we selected all episodes of otitis media acuta among children (< 18 years old). Next, all prescriptions of antimicrobial agents were matched to the distinct OMA episode based on episode number and prescription date. The Dutch GP guidelines only advice the prescription of an antibiotic in case of OMA when no improvement of both the present fever or pain occurs after three days of appropriate pain management. We therefore defined severe symptoms as children which had a reason for encounter for OMA of at least 72 h. In case a child did not have a reason for encounter of at least 72 h, but had received a prescription for antibiotics within this time frame we marked that prescription as being of low-value [31].

3. Repeat opioid prescriptions, without a prior GP visit. Guidelines advice repeat opioid prescriptions only to be prescribed following a consultation with a GP. We therefore included all opioid prescriptions over the examined period in our examination of low-value repeated opioid prescriptions in our assessment. In our analysis of appropriateness, we did not include the initial opioid prescriptions, while these simply cannot be considered repeat prescriptions. Next, the identified GP contacts were matched to each of the repeat opioid prescriptions based on their respective contact and prescription dates. These had to match in order for the repeat opioid prescription to be considered as being appropriate. Repeat prescriptions that did not have a contact associated to them were considered as being of low-value [32].