NAHM Methodology

NOCA worked with the HSE Health Intelligence Unit to establish the National Audit of Hospital Mortality (NAHM). NAHM collates and analyses mortality patterns from publically funded hospitals across the country, using HIPE data, to calculate standardised mortality ratios (SMR). SMR’s are based on the principal diagnosis assigned to a patient when they are admitted to hospital. The SMR is the actual number of patients who die versus the expected number.

Data quality depends on the accuracy and depth of the input done locally. Quality of care is a potential explanation for differences, when the other factors have been taken into consideration but variation in mortality patterns may be explained by:

  • Random (statistical) variation
  • Differences in patient characteristics
  • Issues of data quality
  • Aspects of the quality of care.

NAHM allows each hospital to compare itself to the national norm/average (but not to other hospitals) at three levels:

  • All diagnosis - the full range of diagnostic groupings representing all patients in the hospital sometimes known as HSMR.
  • Diagnostic category - a broad specialty level, such as respiratory.
  • Individual diagnosis - a precise diagnosis level such as pneumonia or acute myocardial infarction.