External validation and comparative analysis of the HOSPITAL score and LACE index for predicting readmissions among patients hospitalised with community-acquired pneumonia in Australia

Objective Community-acquired pneumonia (CAP) is a leading cause of emergency hospitalisations globally and is associated with high readmission rates. Specific score systems developed for all medical conditions such as the HOSPITAL score and the LACE index can also usefully predict CAP readmissions. However, there is limited evidence regarding their performance in the Australian healthcare settings. Methods This multicentre retrospective study analysed adult CAP discharges from two metropolitan hospitals in South Australia between 1 January 2018 and 31 December 2023. Data for determining the HOSPITAL score and the LACE index were derived from electronic medical records. Demographic characteristics of patients readmitted within 30 days were compared with those who were not readmitted. The scores were evaluated for overall performance, discriminatory power and calibration, with discriminatory power assessed using the concordance statistic (C-statistic). Results Over 6 years, 7245 CAP discharges were recorded, with 1329 (18.3%) readmissions within 30 days. The mean (s.d.) age of the cohort was 74.4 (17.8) years. Readmitted patients were more likely to have multiple morbidities and frailty than those not readmitted (P < 0.05). They also had a higher mean number of emergency department presentations and hospital admissions in the previous year and a longer initial hospital stay (P < 0.05). Overall, the mean (s.d.) HOSPITAL score and LACE index were 3.4 (2.1) and 9.3 (3.6), respectively. Among readmissions, 28.4% occurred in patients with a HOSPITAL score >4 (intermediate and high-risk group), while 25.8% occurred in patients in the high-risk LACE category (LACE index > 10). The C-statistic for the HOSPITAL score and LACE index was 0.62 (95% CI 0.61-0.64) and 0.63 (95% CI 0.61-0.65), respectively, with no significant difference in the area under the receiver operating characteristic curves (P > 0.05). Conclusions The predictive abilities of the HOSPITAL score and the LACE index for CAP readmissions are modest and comparable in an Australian setting.