Aim of National Audit of Hospital Mortality
National Audit of Hospital Mortality analyses HIPE data for purpose of identifying and trending mortality in acute hospitals in Ireland.
- Understand and improve the quality of hospital based mortality data
- Stimulate reflection on the quality of overall patient care
Methodology for NQAIS National Audit of Hospital Mortality
- random (statistical) variation;
- differences in patient characteristics;
- issues of data quality;
Similar statistical methodologies are used internationally to account for the first two factors (see below). Data quality depends on the accuracy and depth of coding done locally. Quality of care is a potential explanation for differences when the other factors have been taken into consideration.
Data routinely collected by the hospital inpatient enquiry (HIPE) system and provided by the Healthcare Pricing Office (HPO) of the Health Service Executive is used in the model.
- Age on admission
- Admission type
- Admission source
- Number of emergency admissions in the previous 12 months
- Co-morbidities – using the Charlson Index (modified). The Charlson co-morbidity score consists of 17 medical conditions with attached weights that predict the risk of death within one year on a population basis.
- Indicator of Deprivation
Maternity and Day Case discharges are EXCLUDED.
Calculation of expected deaths per hospital
- “All diagnosis” summary level simply indicates that an unusual mortality pattern has been detected somewhere within the vast range of diagnostic groupings.
- “Diagnostic category” level signals an unusual pattern within a broad “specialty” such as respiratory.
A unique logistic regression equation is computed for each diagnostic group with 40+ deaths and a crude rate is used if <40 deaths.
The expected number of deaths is calculated by summing the predicted number of deaths per CCS group for each institution. The observed number of deaths per institution is extracted from HIPE discharge data. The hospital standardised mortality ratio (SMR) is calculated using the equation:
|SMR =||Observed number of deaths X 100|
|Expected number of deaths|
The SMR indicates the ‘difference from average’. Confidence intervals (95%, 99.8%) are computed around each SMR value. These confidence intervals/control limits indicate its statistical significance having adjusted for the numbers involved. The confidence intervals are wide if the numbers are small, and narrow if the numbers are large.
SMR is supplemented by Cumulative Sum (CUSUM) analysis. Where the SMR aggregates mortality patterns across a defined time period, CUSUM analyses the sequence of discharges as a continuous time series and looks for evidence that the actual mortality pattern may have changed significantly from expected, even over a short time period. The CUSUM control chart is a statistical control chart which detects sequential changes in the difference between the cumulative observed deaths and the cumulative risk-adjusted expected deaths over time – even when relatively small numbers of cases are involved.
NAHM is now live in the following 44 acute hospitals nationally:
|Bantry General Hospital||Cork|
|Cappagh National Orthopaedic Hospital||Dublin|
|Cavan General Hospital||Cavan|
|Cork University Hospital||Cork|
|Galway University Hospitals||Galway|
|Letterkenny University Hospital||Donegal|
|Louth County Hospital||Louth|
|Kilcreene Regional Orthopaedic Hospital||Kilkenny|
|Mallow General Hospital||Cork|
|Mater Misericordiae University Hospital||Dublin|
|Mayo University Hospital||Mayo|
|Mercy University Hospital||Cork|
|Merlin Park University Hospital||Galway|
|Midland Regional Hospital, Mullingar||Westmeath|
|Midland Regional Hospital, Portlaoise||Laois|
|Midland Regional Hospital, Tullamore||Offaly|
|Monaghan General Hospital||Monaghan|
|Naas General Hospital||Kildare|
|Our Lady of Lourdes Hospital, Drogheda||Louth|
|Our Lady’s Children’s Hospital, Crumlin||Dublin|
|Our Lady’s Hospital, Navan||Meath|
|Portiuncula University Hospital||Galway|
|Royal Victoria Eye and Ear Hospital||Dublin|
|Roscommon County Hospital||Roscommon|
|Sligo University Hospital||Sligo|
|South Infirmary Victoria University Hospital||Cork|
|South Tipperary General Hospital||Tipperary|
|St Columcille’s Hospital||Dublin|
|St James’s Hospital||Dublin|
|St John’s Hospital||Limerick|
|St Luke’s General Hospital||Kilkenny|
|St Michael’s Hospital||Dublin|
|St Vincent’s University Hospital||Dublin|
|Temple Street Children’s University Hospital||Dublin|
|University Hospital Kerry||Kerry|
|University Hospital Limerick||Limerick|
|University Hospital Waterford||Waterford|
|Wexford General Hospital||Wexford|