Impact of altering referral threshold from out-of-hours primary care to hospital on patient safety and further health service use: a cohort study

To estimate the impact of altering referral thresholds from out-of-hours services on older patients’ further use of health services and risk of death.Cohort study using patient data from primary and specialised health services and demographic data from Statistics Norway and the Norwegian Cause of Death Registry.Norway491 653 patients aged 65 years and older contacting Norwegian out-of-hours services between 2008 and 2016.Multivariable adjusted and instrumental variable associations between referrals to hospital from out-of-hours services and further health services use and death for up to 6 months.Physicians’ proportions of acute referrals of older, unknown patients from out-of-hours work were used as an instrumental variable (‘physician referral preference’) for their threshold of referral for such patients whose clinical presentations were less clear cut.For older patients, whose referrals could be attributed to their physicians’ threshold for referral, mean length of stay in hospital increased 3.30 days (95% CI 3.13 to 3.27) within the first 10 days, compared with non-referred patients. Such referrals also increased 6 months use of outpatient specialist clinics and primary care physicians. Importantly, patients with referrals attributable to their physicians’ threshold had a substantially reduced risk of death the first 10 days (HR 0.53, 95% CI 0.31 to 0.91), an effect sustaining through the 6-month follow-up period (HR 0.72, 95% CI 0.54 to 0.97).Out-of-hours patients whose referrals are affected by physician referral threshold contribute substantially to the use of health services. However, the referral seems protective by reducing the risk of death in the first 6 months after the referral. Thus, raising the threshold for referral to lower pressure on overcrowded emergency departments and hospitals should not be encouraged without ensuring the accuracy of the referral decisions, ideally through high-quality randomised controlled trial evidence.