A Guide to Using Amenable Mortality as a

System Level Measure

2018

Acknowledgements

This guide has been developed by the Ministry of Health. The authors thank the peer reviewers, both within and outside the Ministry.

Purpose of this Guide

Amenable mortality is used internationally to measure the performance of health systems. Since 1 July 2016 it has been included as one of the six System Level Measures that provide the organising framework for quality improvement and system integration by DHBs and their health system partners through theirdistrict alliances in New Zealand.

This guideexplains the concept of amenable mortality, how it is measured, and how this indicator can be used to improve health system performance.

The guide also includes a brief summary of key amenable mortality statistics for the past 1-2 decades, to familiarise users of this metric with the current situation and recent trends in this performance measure.

The guide may be used by district alliances to guide the development of their System Level Measure Improvement Plans.

Contents

Introduction

The System Level Measures Framework

The Amenable Mortality construct

Measurement and monitoring

High level operational definition

Inclusion and exclusion criteria

Current codelist (as at 1 July 2016)

Table 1: Current amenable mortality codelist (July 2016)

Mortality data

Population data

Standardisation of amenable mortality rates

Reporting

Updating the amenable mortality indicator

Impact of the 2016 update of the amenable mortality codelist

Commencement date

Interpreting amenable mortality rates for use as a System Level Measure

Improving amenable mortality rates: the role of contributory measures

Key findings 2006 – 2014

Key insights

Appendix 1 - technical notes on Standardisation

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Version: January 2018

Introduction

The System Level Measures Framework

This Frameworkaims to improve health outcomes for people by supporting DHBs to work in collaboration with their health system partners (primary, community and hospital) using specific quality improvement measures. It provides a foundation for continuous quality improvement and system integration.

System Level Measures align with the five themes of the Health Strategy and other national strategic priorities such as Better Public Service Targets. They have a focus on children, youth and vulnerable populations. System Level Measures are part of the DHB annual planning process and provide an opportunity for DHBs to work with their primary, secondary and community care partners to improve health outcomes of their local population. They promote better understanding and use of health information, engagement with people in the design and delivery of health services and better health investment in models of care based on local population needs.

The Ministry worked closely with the sector to co-develop the sixSystem Level Measures (SLMs) that together provide a system-wide view of performance. The SLMs engage the health sector broadly (in terms of professions, settings and health conditions) and cover all levels of health care.

The six SLMs are:

  • Childhood Ambulatory Sensitive Hospitalisations rates for 0-4 year olds
  • acute hospital bed days per capita
  • patient experience of care
  • amenable mortality rates
  • babies living in smokefree homes
  • youth access to and utilisation of youth appropriate health services.

Brief definitions and a summary of data sources and statistical methods used to calculate these measures are available in the Measures Library, accessible via the Health Quality Measures New Zealand website ( The Measures Library also lists and defines key ‘contributory measures’, which are more specific and local measures of factors that can contribute to improvement in the SLMs.

The Amenable Mortality construct

Amenable mortality is widely accepted internationally as a valid and reliable indicator of health system performance. In New Zealand this metric is especially relevant to the ’value and high performance’ theme of the refreshed New Zealand Health Strategy, and can serve to identify potential areas of concern for more detailed investigation (seeThe Guide to using the System Level Measures Framework; andSaving Lives: Amenable mortality in New Zealand 1996 – 2006).

The idea underpinning the amenable mortality construct is that the contribution of health care to improvement in population health can be quantified by counting deaths from causes avoidable through health system intervention.Such interventions may work by reducingincidence (prevention of the underlying conditionto reduce the number of new cases) or by reducing case fatality (treatment leading to cure or delay in progression of the underlying condition).

The rate at which deaths from these selected causes continue to occur should then reflect the performance of the health system, at least in so far as avoidance of fatal outcomes is concerned.

There are two refinements to this broad concept:

  • Prevention can be achieved by providing clinical preventive services such as immunisation and screening to individuals, or by services directed to populations collectively, such as legislation on vehicle standards or taxation of tobacco. The healthcare system cannot directly controlintersectoral interventions aimed at the social determinants of health. So only deaths amenable to clinical interventions, preventive or therapeutic andprovided to individuals are included.
  • Death is of course inevitable, so only deaths (from avoidable causes) occurring at a younger age than expected (‘premature’ deaths) should be included.

A more casual definition of amenable mortality is ‘unnecessary,untimely deaths’.

In reality, not all deaths from any ‘amenable’ cause can be avoided – the relevant intervention may have limited efficacy; the person may have presented late in the disease process; the person may fail to respond to the intervention for genetic, immunologic or other reasons; the person may be frail or have serious co-morbidities; the person may not tolerate or may refuse or fail to adhere to the prescribed treatment. So the concept refers to the expectation that the population mortality rate from an amenable cause will be substantively reduced, not necessarily eliminated.

Similarly, the requirement that deaths be ‘premature’ is not readily operationalised. The simplest approach (which is currently the one used) is to define an arbitrary upper age limit for the death to qualify as a ‘premature’ death – acknowledging that this is inevitably ageist.

An even more basic limitation of the metric arises from the reality that much healthcare is not aimed at life extension at all, but rather at improving health related quality of life. This dimension of health system performance cannot be captured by a mortality metric.

Finally, the binary classification of causes of death as ‘amenable’ or ‘not amenable’ poses operational challenges of its own. Two widely used lists exist: Nolte & McKee and Tobias & Glover. In New Zealand the Tobias & Glover list is used.

Tobias & Glover developedtheir list through a combination of expert judgement (using a panel of clinicians and public health physicians), trend analysis (looking for discontinuities in mortality trends following introduction of new interventions), and systematic review of RCTs (to identify potentially effective interventions). Table 1 shows the current causelist with the rationale for each included cause.

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Version: January 2018

Table 1 Current Amenable Mortality Causelist: Rationale

Cause of death / Rationale for inclusion
Pulmonary tuberculosis / Advances in directly observed treatments (DOTS)
Meningococcal disease / Advances in antibiotics and intensive care
Pneumococcal disease / Advances in antibiotics and intensive care
Hepatitis C / Advances in antiviral drugs
HIV / AIDS / Advances in antiretroviral drugs (HAART)
Stomach cancer / Advances in diagnosis (endoscopy), surgery and adjuvant therapy (combination chemotherapy including fluorouracil), and advances in antibiotics to eliminate H. pylori infection
Rectal cancer / Advances in radical surgery and adjuvant therapy (oxaliplatin)
Bone and cartilage cancer / Advances in surgery and adjuvant therapy (chemo-radiotherapy)
Melanoma of skin / Advances in early detection and adjuvant therapy
Female breast cancer / Advances in mammographic screening, estrogen receptor assays, and adjuvant therapy (tamoxifen and congeners)
Cervical cancer / Advances in: screening, surgery, adjuvant therapy (concurrent chemo-irradiation)
Uterine cancer / Advances in early case detection and surgery
Prostate cancer / Advances in anti-androgens and other adjuvant therapy
Testis cancer / Advances in chemotherapy (cisplatin)
Thyroid cancer / Advances in diagnosis and adjuvant therapy
Hodgkin lymphoma / Advances in high dose combination chemotherapy and peripheral blood stem cell transplantation
Acute lymphoblastic leukaemia / Advances in chemotherapy (combination chemotherapy including 6-mercaptopurine, vincristine and prednisone) (<45 only)
Complications of pregnancy / Advances in obstetric care
Complications of perinatal period / Advances in neonatal intensive care and surfactant therapy
Cardiac septal defect / Advances in diagnosis, surgery (including cardiopulmonary bypass and DHCA)* and paediatric intensive care
Diabetes / Advances in diagnosis, insulins, oral hypoglycemics, tight glucose and blood pressure control, and models of care
Valvular heart disease / Advances in diagnosis (cardiac catheterisation), surgery, and artificial valve replacement
Hypertensive diseases / Advances in antihypertensive drugs (especially ACE inhibitors and calcium antagonists)
Coronary heart disease / Statins (and other drugs for secondary prevention), thrombolysis, advances in reperfusion therapy and coronary care units
Pulmonary embolism / Advances in diagnosis and anticoagulation
Atrial fibrillation & flutter / Advances in rhythm control (drugs, pacemakers) and anticoagulation
Heart failure / Advances in diagnosis, and in combined therapy including ACE inhibitors
Cerebrovascular diseases / Advances in imaging, antihypertensives, atrial fibrillation (AF) management, and dedicated stroke units
COPD / Advances in antibiotics, bronchodilators, and physiotherapy
Asthma / Advances in bronchodilators, steroids and intensive care
Cholelithiasis / Advances in lithotripsy
Renal failure / Advances in dialysis and renal transplantation (including advances in immunosuppression)
Peptic ulcer disease / Advances in drug treatment (cimetidine and other H2 receptor antagonists) and H. pylori eradication
Land transport accidents excluding trains / Advances in emergency transport and trauma care
Accidental falls on same level / Advances in osteoporosis treatment and orthopaedic care
Fire (burns) / Advances in early excision and skin grafting
Suicide / Advances in antidepressant therapy

*Deep hypothermia cardiac arrest

Measurement and monitoring

High level operational definition

Amenable mortality is defined as premature deaths (deaths under age 75) that could potentially be avoided given effective and timely healthcare. That is, early deaths from causes (diseases or injuries) for which effective health interventions exist and are accessible to everyone in need (in New Zealand).

Not all deaths from these causes could be avoided in practice (for example, because of co-morbidity, frailty and patient preference). However, a higher than expected rate of such deaths in a DHB (for the total population or a subgroup such as Māori) may indicate that access to, or quality of, care could be improved.

Inclusion and exclusion criteria

A specific intervention, package of interventions, or model of care (hereafter 'intervention') must be identified and linked to a specific cause of death (COD). There must be a clear ICD code for the COD and reporting and coding must be of high quality.

The intervention must be a medical or surgical intervention delivered by or under the direction of a clinician (doctor or nurse) to individuals (patients or well persons at risk) in a healthcare setting (including the home). Note that the intervention may involve screening, diagnosis or rehabilitation, as well as treatment. Public health interventions delivered collectively to populations (egfood safety laws, tobacco taxes, safe sex social marketing campaigns) are excluded so that the measure reflects access to and effectiveness of health care rather than wider social systems.

The intervention must have been introduced and become generally accessible to New Zealand patients or at risk populations within the past 40-50 years (iepost 1960).Interventions introduced many decades ago are likely to have become diffused even in poorly performing health systemsso such interventions provide no comparative information regarding current health system performance.

The intervention must have either already reduced under 75 mortality (in the relevant New Zealand subpopulation or patient group) by more than 30%, or have been shown in randomized controlled trials (RCTs) or high quality observational studies to be capable of such mortality reduction within five years of universal coverage being achieved[1].

The linked COD must account (currently) for >0.1% of all under 75 deaths (roughly 10 deaths per year)[2].

Current codelist (as at 1 July 2016)

The current list of amenable causes of death (Table 1) was updated by an expert panel in June 2016. The updated list comprises 38 conditions, grouped into six super-categories:

  • infections
  • maternal and infant conditions
  • injuries
  • cancers
  • cardiovascular diseases and diabetes
  • other chronic diseases.

In analysis, it can be more useful to use these super categories as the rates of individual conditions may be too small to make much impact on the overall amenable mortality rate. This should not prevent consideration of where an intervention may make a significant impact on the rates of specific conditions.

Table 1: Current amenable mortality codelist (July 2016)

Group / Condition / ICD-10-AM-VI
Infections / Pulmonary tuberculosis / A15-A16
Meningococcal disease / A39
Pneumococcal disease / A40.3, G00.1, J13
Hepatitis C (HCV) / B17.1, B18.2
HIV/AIDS / B20-B24
Cancers / Stomach cancer / C16
Rectal cancer / C19-C21
Bone and cartilage cancer / C40-C41
Melanoma of skin / C43
Female breast cancer / C50
Cervical cancer / C53
Uterine cancer / C54, C55
Prostate cancer / C61
Testis cancer / C62
Thyroid cancer / C73
Hodgkin lymphoma / C81
Acute lymphoblastic leukaemia (For ages 0-44 only) / C91.0
Maternal and infant disorders / Complications of pregnancy / O00-O96, O98-O99
Complications of perinatal period / P01-P03, P05-P94
Cardiac septal defect / Q21
Cardiovascular disorders and diabetes / Diabetes / E10-E14
Valvular heart disease / I01, I05-I09, I33-I37
Hypertensive diseases / I10-I13
Coronary heart disease / I20-I25
Pulmonary embolism / I26
Atrial fibrillation & flutter / I48
Heart failure / I50
Cerebrovascular diseases / I60-I69
Other chronic disorders / Chronic obstructive pulmonary disease (COPD) / J40-J44
Asthma / J45-J46
Cholelithiasis / K80
Renal failure / N17-N19
Peptic ulcer disease / K25-K27
Injuries / Land transport accidents excluding trains / V00-V04, V06-V14, V16-V24, V26-V34, V36-V44, V46-V54, V56-V64, V66-V74, V76-V79, V80.0-V80.5, V80.7-V80.9, V82-V86, V87.0-V87.5, V87.7-V87.9, V88.0-V88.5, V88.7-V88.9, V89, V98-V99
Accidental falls on same level / W00-W08, W18
Fire (burns) / X00-X09
Suicide / X60-X84

Mortality data

The numerator data for the amenable mortality metric is extracted from the Mortality Data Collection. The Mortality Data Collection uses information from a variety of sources (including death certificates, hospital separations summaries, patient records, coronial reports and police reports) to code the underlying cause of death (COD) for every death in New Zealand. The underlying cause is defined as the cause that initiated the train of events leading to the death.

Currently, COD is coded using ICD-10 amenable mortality version VI. 2014 will be the first year coded in ICD-10-AM-VIII. Note that the Ministry changes versions regularly, and at some point ICD-10 will be replaced by ICD-11.

To calculate amenable mortality, all deaths registered in New Zealand in the relevant calendar year with underlying COD included in the current version of the amenable mortalityCodelist, where the deceased was aged 0-74 years at date of death (with some exceptions within this broad age range), are extracted.

Variables extracted from the Mortality Data Collection for each relevant death include:

  • NHI
  • DHB of residence (and linked NZDepdecile)
  • Date of birth (and age in five-year age bands)
  • Date of death
  • Sex
  • Ethnicity (prioritised)
  • Underlying cause of death (ICD-10-AM three or four digit code as applicable)

Population data

Denominator data to calculate amenable mortality rates are the national or DHB usually resident populations derived from projections the Ministry gets annually from Statistics New Zealand(SNZ) for the PBFF[3]. The ethnic denominators are based on prioritised ethnicity, to align with the numerator data. Both these denominators and the NZDepdecile or quintile denominators are derived internally within the Ministry of Health from the SNZ projections; they are not available directly from SNZ.

Variables extracted include:

  • Year
  • DHB
  • Age 0-74 in five-year age bands
  • Sex
  • Ethnicity
  • NZDepdecile

Standardisation of amenable mortality rates

Crude amenable mortality rates (along with 95% or 99% confidence intervals) are calculated by dividing the amenable mortality count by the corresponding population count (with confidence intervals estimated in the usual way). However, these crude rates do not allow fair comparison of one DHB with another, or the same DHB with itself over time, because of variation in the underlying population age and sex structure, ethnic mix or socioeconomic (ie: deprivation) distribution.

To control for confounding by these socio-demographic variables, a combination of stratification and standardisation is employed. Alternatively, regression modelling may be used. This report used the WHO World Population as the reference for the age weights (for all ages). This standardization method has its limitations (for further information, see appendix 1) but was selected to allow international comparison if needed and for being consistent with other indicators and Ministry publications.

Reporting

Reports are made available to DHBs annually, in or around February of each year (subject to mortality data being available in December). DHBs are provided with a rolling five year data set, covering the period from two to seven years prior to the current calendar year.

It takes several years for some coronial cases to return verdicts. Given the significant impact these cases can have on some causes of death,estimates for the amenable mortality indicator are not available until approximately two years after the end of the year of death registration.

Updating the amenable mortality indicator

The amenable mortalitycodelist requires regular updating:

  • Medical advances mean that some CODs not previously classified as amenable will now meet all inclusion criteria.
  • Mortality from some CODs currently included as amenable will fall so low that no further fall is possible; nor would any recurrence in mortality from these conditions be expected barring total collapse of the health system. While leaving such CODs on the list does no harm, it adds nothing either and increases ‘clutter’ and opportunity for error.

Any change to thecodelist creates a discontinuity in the time series that makes interpreting trends in amenable mortality rates more difficult. The frequency of updating needs to balance these opposing tensions. For that reason, the codelistis updated at 5-10 year intervals.