What impact will implementation of ICD-10 have on mortality statistics by cause in the elderly? Clare Griffiths Health and Care Division Office for National Statistics

Mortality Data Collected for England and Wales by ONS from civil registration of deaths info on cause of death comes from medical certificate of cause certain cases referred to a coroner - info sent direct to registrar

Classification of cause of death Using International Classification of Diseases Since 1979 ICD-9 Since 2001 ICD-10 Data not yet published in ICD-10 Classification important for assessing health of population Change particularly affects elderly

ICD-10 for Mortality in England and Wales From January 2001 more codes - detail move conditions between chapters change underlying cause of death selection rules all these produce artefacts

Underlying cause of death …’the disease or [external cause of] injury which initiated the train of morbid events leading directly to death….’ For public health preventing death and illness leading to death

Cause of death certificate direct causeIa carcinomatosis due to b prostate cancer due to c other contributing causeII hypertension ……………………………………………... Underlying cause of death - prostate cancer

General Principle and Rule 3 - ICD-9 / ICD-10 General Principle “ When one or more conditions is entered on the certificate, the condition entered alone on the lowest used line of Part I should be selected only if it could give rise to all the conditions entered above it” Rule 3 “If the condition selected by the General Principle or by Rule 1 or Rule 2 is obviously a direct consequence of another reported condition, whether in Part I or Part II, select this primary condition.”

Cause of death Ia bronchopneumonia b c II Alzheimer’s disease UCD bronchopneumonia ICD-9 Alzheimer’s disease ICD-10

Age standardised mortality rates in Women in England & Wales 1968 to 1999 by selected chapters of ICD-8 and ICD-9

Bridge coding Identify artefacts due to classification change independent coding to ICD-9 and ICD-10 all deaths registered in 1999 original text and amendments routine coding procedures/ rules –US Software, clerical for inquests

Why bridge code? Measure effect of change in classification Allow adjustment of rates Interpret time trends in cause-specific mortality in routine statistics

Bridge coding outputs comparability ratios for each cause –eg IHD deaths in ICD-10/ IHD deaths in ICD-9 stratified by age, sex? –do CRs vary significantly? –confidence limits ‘adjusted rates’ for old trend data –‘new’ baselines and targets

IHD mortality rates in women, E&W, 1999: by age, ICD-9, ICD-10 and comparability ratio

Cancer mortality rates in women, E&W, 1999: by age, ICD-9, ICD- 10 and comparability ratio

Stroke mortality rates in men, E&W, 1999: by age, ICD-9, ICD-10 and comparability ratio

Pneumonia mortality rates in men, E&W, 1999: by age, ICD-9, ICD-10 and comparability ratio

Pneumonia ASMR women, E&W as published and adjusted for changes in classification

Other causes Suicide is based on verdict and unlikely to change Injuries (including falls): changes in the axis of classification

Effects and Plans Cause-specific mortality rates will change Comparability ratios available on the National Statistics website from Spring 2002 Standard shortlists, Our Healthier Nation New baselines and targets

Any questions? Queries on ICD-10 & deaths data – Queries on other ICD issues More details in Health Statistics Quarterly No 8 downloads/theme_health/HSQ8Book.pd f Forthcoming in HSQ 13 February 2002