Case Ascertainment Information for EmLap Cases

NELA+ monitors the estimated case ascertainment from each hospital site to ensure published NELA+ reports reflect the entire emergency laparotomy population. Case ascertainment is calculated by dividing the number of cases submitted to NELA+ by the expected total number of emergency laparotomy cases at your site.  If you don’t input your data in real time, your case ascertainment figures may be lower than what we would expect.

The expected total number of emergency laparotomies is identified from national-level data from NHS England (Hospital Episode Statistics [HES] data) and Digital Health and Care Wales (Patient Episode Database Wales [PEDW] data). For Northern Ireland, this information is collated locally and shared with the central NELA+ team. HES/PEDW data is submitted to NHS England/Digital Health and Care Wales by a hospital’s coding department. HES/PEDW records include information on a patient’s mode of admission, diagnoses and procedures for an inpatient hospital stay.

NELA+ uses an algorithm to search HES/PEDW data*. To be identified, the algorithm requires:

• The patient to be admitted as an emergency (elective laparotomies are not included in NELA+)

• OR a patient admitted electively who has a second laparotomy (unplanned returns to theatre after elective surgery can meet the NELA+ inclusion criteria)

• An OPCS code which shows the patient underwent a procedure which matches operations in the NELA+ inclusion criteria. The full list of OPCS codes which meet NELA+ criteria is available here.

• Further steps which exclude specific groups of patients based on hierarchy of codes. For example, a patient who undergoes bowel resection incidental to a ruptured AAA repair does not meet NELA+ inclusion criteria, and this record is excluded from the expected submissions.

If you have been monitoring monthly reports and think your case ascertainment is low, there may be some simple errors to exclude:

• Review your NELA+ data entry process. Ensure those responsible for data entry are familiar with the NELA+ inclusion and exclusion criteria, available in the tab below.

• Review admission process for your elective patients. If patients are attending for elective gastrointestinal surgery but being coded to HES/PEDW as ‘emergency’ admissions, they will wrongly appear to be cases who meet NELA+ eligibility.

• Review the patients who have been allocated one of the NELA-eligible OPCS codes by your coding department. Do these codes accurately reflect the patient’s actual operation?

Outliers based on Case Ascertainment

NELA+ has recently updated our outlier policy to include outliers based on case ascertainment. NELA+ will formally notify sites if they are potentially going to be named as an outlier. We try to contact sites in advance of this, so they have plenty of opportunity to look into their low case ascertainment.  NELA+ will contact sites informally to let them know if their case ascertainment seems low throughout the year and we strongly recommend you take a look at your cases if we do so. You can also monitor your case ascertainment via our monthly reports, which include an estimate of current case ascertainment in comparison to historic HES/PEDW data.

*HES/PEDW data is not available to the NELA+ team in real-time. To allow us to flag sites which appear to be struggling with case ascertainment, we use an estimate based on previous years’ data. In general, the number of emergency laparotomies at one site remains stable year-on-year; however, if there has been a significant restructuring of services this may not be the case. Final calculations of case ascertainment in annual reports are calculated using that year’s actual HES/PEDW data.

Instructions for calculating how your hospital's in-patient mortality rate compares to the expected mortality based on preoperative risk assessment, as well as a working example.

• Observed-Expected Mortality Ratio Calculation Explanation

• Observed-Expected Mortality Ratio Calculation Worked Example