Differential behaviour of a risk score for emergency hospital admission by demographics in Scotland - a retrospective study

The Scottish Patients at Risk of Re-Admission and Admission (SPARRA) score predicts
individual risk of emergency hospital admission for approximately 80% of the Scottish
population. It was developed using routinely collected electronic health records, and is
used by primary care practitioners to inform anticipatory care, particularly for
individuals with high healthcare needs. We comprehensively assess the SPARRA score
across population subgroups defined by age, sex, ethnicity, socioeconomic deprivation,
and geographic location. For these subgroups, we consider differences in overall
performance, score distribution, and false positive and negative rates, using causal
methods to identify effects mediated through age, sex, and deprivation. We show that
the score is well-calibrated across subgroups, but that rates of false positives and
negatives vary widely, mediated by various causes including variability in demographic
characteristics, admission reasons, and potentially differential data availability. Our
work assists practitioners in the application and interpretation of the SPARRA score in
population subgroups.