Table 4. Definitions and data sources for NHS cost outcome measures.

Cost Outcome	Definition	Source of data
Use of renal replacement therapy (resource use measured in days)	Use of:       -      Haemofiltration       -      Haemodiafiltration       -      Haemodialysis       -      Peritoneal dialysis	HL7 data aggregated within the Streams-AKI data processor/Trust submissions to the Health Episode Statistics- Admitted Patient Care database, and Payment by Results/local tariffs at the Trust
Length of stay on a regular inpatient ward	Length of stay outside:       -      AKU       -      HDU       -      ITU During index admission	HL7 data aggregated within the Streams-AKI data processor, and Payment by Results/local tariffs at the Trust
Length of stay in high acuity bed	Length of stay inside:       -      AKU       -      HDU       -      ITU During index admission	HL7 data aggregated within the Streams-AKI data processor, and Payment by Results/local tariffs at the Trust
Readmission to hospital	Readmission to hospital in 30 days following index admission discharge date	HL7 data aggregated within the Streams-AKI data processor, and Payment by Results/local tariffs at the Trust
Staffing costs	An estimate of staffing cost associated with the delivery of usual care vs. the Streams-AKI care pathway	Staff observation exercise
Cost of investigations	An estimate of costs associated with interventions made and/or investigations ordered as a result of AKI	Staff observation exercise, HL7 data aggregated within the Streams-AKI data processor