'Missingness' in health care: Associations between hospital utilization and missed appointments in general practice. A retrospective cohort study.

Objectives Are multiple missed appointments in general practice associated with increased use of hospital services and missingness from hospital care? This novel study explores this in a population representative sample for the first time. Design, setting, participants A large, retrospective cohort (n = 824,374) of patient records from a nationally representative sample of GP practices, Scotland, 2013-2016. Requested data were extracted by a Trusted Third Party for the NHS, anonymised and linked to a unique patient ID, in the NHS Safehaven for analysis using established NHS Scotland linkage. We calculated the per-patient number of GP missed appointments from individual appointments and investigated the likelihood of hospital appointment or admission outcomes using a negative binomial model offset by number of GP appointments made. These models also controlled for age, sex, Scottish Index of Multiple Deprivation (SIMD) and number of long- term conditions (LTCs). Main outcome measures Hospital attendance: Outpatient clinic attendances; hospital admissions; Emergency Department (ED) attendances. Hospital missingness: 'Did not attend' (DNAs) outpatient clinic appointments, 'irregular discharges' from admissions, and 'left before care completed' ED care episodes. Results Attendance: Patients in the high missed GP appointment (HMA) category were higher users of outpatient services (rate ratio (RR) 1.90, 95% confidence intervals (CI) 1.88-1.93) compared to those who missed none (NMA) with a much higher attendance risk at mental health services (RR 4.56, 95% CI 4.31-4.83). HMA patients were more likely to be admitted to hospital; general admissions (RR 1.67, 95% CI 1.65-1.68), maternity (RR 1.24, 95% CI 1.20-1.28) and mental health (RR 1.23, 95% CI 1.15-1.31), compared to NMA patients. Missing GP appointments was not associated with ED attendance; (RR 1.00, CI 0.99-1.01). Missingness: HMA patients were at greater risk of missing outpatient appointments (RR 1.62, 95% CI 1.60-1.64) than NMA patients; with a much higher risk of non-attendance at mental health services (RR 7.83, 95% CI 7.35-8.35). Patients were more likely to leave hospital before their care plan was completed-taking 'irregular discharges' (RR 4.56, 95% CI 4.31-4.81). HMA patients were no more at risk of leaving emergency departments 'without care being completed' (RR1.02, 95 CI 0.95-1.09). Conclusions Patients who miss high numbers of GP appointments are higher users of outpatient and inpatient hospital care but not of emergency departments, signalling high treatment burden. The pattern of 'missingness' is consistent from primary care to hospital care: patients who have patterns of missing GP appointments have patterns of missing many outpatient appointments and are more likely to experience 'irregular discharge' from in-patient care. Missingness from outpatient mental health services is very high. Policymakers, health service planners and clinicians should consider the role and contribution of 'missingness' in health care to improving patient safety and care.