How are expected cases calculated?
SSNAP uses HES data from previous years to calculate a denominator for each routinely admitting team to set “expected” numbers of future admissions per year. SSNAP wishes to check and validate the number of records each team has submitted to the audit in previous years against the contemporaneous HES for that time period, and to set expected figures for the upcoming year. Comparing the number of SSNAP admissions to the expected figure for each team is an important validation for SSNAP, and acts as a measure of case ascertainment for England. For Northern Ireland and Wales this is derived from previous data sources and on-going data submissions.
Case ascertainment is calculated differently based on the type of team:
a) Routinely admitting acute teams
The estimated number of admissions and discharges in any one reporting period (Expected cases) are provided to all routinely admitting teams.
It is required that teams submit all stroke patients with a primary diagnosis of stroke. Case ascertainment is calculated based on the proportion of patient admissions (locked to 72 hours) AND proportion of discharges (locked to discharge or transferred to another team) against the expected number in any one reporting period. The average of these two percentages is then used for the overall case ascertainment banding. To ensure no downward adjustment of the overall SSNAP level teams must ensure that their case ascertainment band is ≥ 90%. 75% of the expected number of cases is the minimum required in order to receive named team results.
To view your current expected cases, follow this link once logged into the SSNAP webtool, and download "Expected cases".
b) Non-routinely admitting inpatient teams and non-inpatient teams
For non-routinely admitting teams, HES projections have not been used. A proxy has been generated comparing the number of patients arriving at a team with the number of patients leaving the team in a reporting period. Teams should always ensure that all discharges within a reporting period are locked prior to the quarterly locking deadline.
Click here to see how the SSNAP scoring is calculated and how case ascertainment can cause negative adjustment
How to amend your expected cases (routinely admitting teams only)
The number of stroke patients seen over time may fluctuate particularly when a service undergoes reconfiguration. If a team’s number of cases varies by more than 10% then the SSNAP team may be able to adjust the expected number of cases. Where this applies teams are encouraged to contact the SSNAP helpdesk as soon as possible.
Evidence of the total number of stroke cases coded as I61, I63 and I64 should be provided for a minimum of three months. This coded data is ordinarily supplied by the team's information or coding department.
Please make sure the data provided contains the ICD-10 code and the admission and/or discharge date for the patient. Please do not send any patient identifiable information, including NHS number, name, address, GP details, etc.
All coded data must be sent by the data-locking deadline. It is not possible to change the expected figure after the deadline has passed.