To evaluate the impact of video use in out-of-hours primary care (OOH-PC) telephone triage by examining how triage outcomes (ie, ended by telephone, clinic consultation or home visit) changed during a period with video service failure.

Observational register-based study, using periods of video service failure as a randomisation mechanism for a controlled study.

OOH-PC in four of the five Danish regions.

All telephone triage contacts to the OOH-PC call centres between April 2020 and December 2021.

Video service failures resulted in a subset of telephone triage contacts without the option of using video as a triage tool. Video service failures were identified algorithmically based on observed periods without video use.

Proportion of telephone triage contacts with clinic consultations or home visits as triage outcome during a period of video service failure compared with matched reference telephone triage contacts taking place during normal service (1:10), presented as risk ratios (RR) with 95% CI).

The algorithm identified 6605 telephone triage contacts during video service failure. Compared with matched contacts during normal service, these had a 15% higher risk of resulting in a clinic consultation (RR: 1.15, 95% CI 1.09 to 1.20). This effect was primarily isolated to the year 2021 (RR: 1.23, 95% CI 1.16 to 1.31) compared with 2020 (RR: 1.05%, 95% CI 0.97 to 1.13). Video service failure did not significantly affect the risk of a home visit.

Results strongly suggest that the unavailability of the video service is likely to significantly increase the number of clinic consultations in OOH-PC as a triage outcome. Whether this effect is likely to persist in the long term remains unclear.