Out-of-hours C-reactive protein point-of-care testing and its association with long-term healthcare-seeking

BACKGROUND: Increased diagnostic testing may contribute to clinically unnecessary healthcare-seeking. AIM: To analyse whether patients exposed to general practitioners (GPs) who frequently use C-reactive protein point-of-care testing (CRP-POCT) have different long-term use of out-of-hours (OOH) primary care services. DESIGN AND SETTING: Register-based time-to-event analysis of OOH primary care in the Central Denmark Region (population 1.3 million). The service functions as gatekeeper to hospital care. The GPs work a limited number of shifts per month. METHODS: All in-person clinic consultations at the OOH clinics from 2014 to 2017 were included. The exposure was the consulted GP's adjusted tendency to perform CRP-POCT relative to peer GPs, based on the latest 50 consultations. Covariates included patient characteristics, GP activity level and experience in OOH care, and time of consultation. Hazard ratios (HRs) for revisiting OOH primary care were estimated. RESULTS: A total of 862,733 consultations were included. The proportion of consultations involving CRP-POCT increased from 12% in 2014 to 19% in 2017. Kaplan-Meier estimates showed that it took 2.5 years before half of the patients had returned for an OOH consultation. The adjusted HR for revisiting was 1.038 (95% CI = 1.023 to 1.054) for patients seen by a GP with twice the average CRP-POCT use or higher, compared with those seen by a GP with average use. CONCLUSION: Being seen by a GP with a high propensity to use CRP-POCT was associated with increased long-term OOH all-cause healthcare-seeking. This may reflect effects of CRP-POCT itself, correlated GP characteristics, or both.