Selecting hospital records for injury surveillance:

Australia as an example

James HarrisonResearch Centre for Injury Studies

Adelaide, South AustraliaSeptember 2006

Acknowledgements

Jesia Berry

Geoffrey Henley

Malinda Steenkamp

Clare Bradley

Context The purpose is national injury surveillance

especially for primary prevention of injury in the general community also interest in outcomes, costs, injury & other complications of care

Australia’s federal political system shapes the hospital system & its data the 8 states & territories operate most of the hospitals the Commonwealth raises and distributes most of the money the public money is allocated by a system using Diagnosis Related Groups (DRGs)

Mixed public-private hospital system acute care of serious injury is mostly in the public sector

About 350 thousand admitted injury cases / year +/- a bit, depending on definition, selection criteria, etc. (nearly) complete annual national unit-record files (for public and private hospitals) each record = an episode of in-patient care (not a person or a case) records include codes for Principal & Additional diagnoses & external causes ICD-10-AM (Australian Modification) since 1998-99; new edition each 2 years

Purpose How much (serious) injury occurs in Australia?

What are the injuries? Diagnoses, body parts affected

How does injury occur? External causes, etc

How is it distributed? By person

age, sex, Indigenous status, etc.

By place State/territory, remoteness, etc.

Over time trends

What are its consequences? Survival, hospital utilisation, rehabilitation, quality of life, economic costs, etc

Background Usable national hospital data not available until early to mid 1990s

Improvement largely driven by change to DRG-based payment for public hospital services

Our early reports (late 1990s) Much time spent learning about the data Very cautious about claiming to be able to provide reliable information on trends and

differences This experience prompted development of a conceptual approach and plan

Technical review & documentation of current NHPA indicators and data sources (2002)

Our thinking was influenced by the Injury ICE

Commenced a program of development projects

Recent reports 2001-02, 2003-04 (under review), 2004-05 (early stages of preparation) More comprehensive and coherent Each has similar structure, adding refinement and features in each edition Largely restricted to data since late 1990s

(Quality seems to be better; avoids complications of bridging ICD-9-CM to ICD-10-AM)

Case selection criteria Issues considered in specifying criteria:

Period

Place/person

Condition

Counting incident cases once and only once

Minimising effect of variation in probability of detection of an incident case

Case selection criteria Issues considered in specifying criteria:

Period

Place/person

Condition

Counting incident cases once and only once

Minimising effect of variation in probability of detection of an incident case

Case selection criteria Issues considered in specifying criteria:

Period Year of separation (~discharge). Ideally, period of injury.

Place/person (Almost) all acute hospitals in Australia. Some numerator-

denominator mismatch (inward & outward visitors, etc).

Condition Counting incident cases once and only once

Using an approximate method; working on person-linkage

Minimising effect of variation in probability of detecting an incident case

Some use of ICISS; interest in p(admission)

Selection criteria: condition (1) Injury surveillance

… so we first select cases in terms of injury (then external causes)

‘Injury’ presently specified as S00-T75, T79 Includes ‘anatomical’ trauma, burns, poisoning and ‘certain early

complications of trauma’ (T79)

Similar to the STIPDA ICD-9-CM specification (except we have omitted late effects/sequelae here, since our aim is to estimate incidence of new cases in a period).

We call this ‘Community injury’, a term used to distinguish this set of cases, especially from the main other subject of ICD-10 Chapter 19, Complications of surgical/medical care, nec (T80-T88).

Can some conditions codable to other chapters of ICD reasonably be regarded as in-scope for injury? Probably so. (We’re discussing this with colleagues in Australia).

Selection criteria: condition (2) We presently include only records in which

Principal Diagnosis is in the range S00-T75, T79 There is good reason to include these, since injury was the

main reason for the episode in hospital.

What about records with at least one code in this range, but not as Principal Diagnosis? These are commonly for episodes of rehabilitation, usually following on from an acute care episode. Including them all would certainly inflate estimates of incident cases. We will review handling of this group when better person-linked files are available to us.

Selection criteria: condition (3) Injury cases are counted whether or not

the record includes an external cause code

Australian coding standards require that all cases meeting our definition of injury should have at least one external cause code.

Nearly all cases that meet other criteria do so: 99.9% in 2003-04, up from about 97% in 2001-02.

We count the rest as ‘injury cases’, though the lack of external cause codes limits analysis.

Selection criteria: condition (4) Handling of ambiguous records

Our recent reports on hospitalised injury have focused on Community injury, but have included summary information on other cases coded to Chapter 19 of ICD-10-AM, chiefly Complications of surgical/medical care coded to T80-T88.

A small proportion of records were ambiguous, having

Principal Diagnosis = Community injury and first External cause code = Complications, or

Principal Diagnosis = Complications and first External cause code = Community injury.

We are now (2003-04 report) assigning these on the basis of Principal Diagnosis.

Selection criteria for cases due to injury and poisoning, Australia 2003–04

Selection criteria Persons

Community injury (ICD-10-AM Principal Diagnosis range S00–T75, T79), and

lack any external cause code 361

have a first reported external cause code of Complications of surgical and medical care 1,640

have a first reported external cause code in the range V01–Y36, Y85–Y87, Y89 342,848(a)

Total case numbers for Community injury 344,849(a)

Complications of surgical and medical care (ICD-10-AM Principal Diagnosis range T80–T88), and

lack any external cause code 100

have a first reported external cause code of Community injury 357

have a first reported external cause in the range Y40–T84, Y88 67,061

Total case numbers for Complications of surgical and medical care 67,518

Case numbers where Principal Diagnosis is in ICD-10-AM Chapter XIX Injury and poisoning but is not classified as Community injury or Complications of surgical and medical care 4,441

All separations with Principal Diagnosis in the ICD-10-AM range S00–T98 416,808(b)

Includes (a) 3, and (b) 3 separations for which sex was not reported.

Community injury, Australia 1999–00 to 2003–04 Age-standardised rates

0

500

1,000

1,500

2,000

2,500

3,000

1999–00 2000–01 2001–02 2002–03 2003–04

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Approach to the task recognise that our data, knowledge and methods all have

substantial limitations

try to make good use of the available data

try to detect, create and make good use of opportunities to improve data, methods and our knowledge of them

don’t expect to do everything at once, but try to improve what we do with each new publication

are willing to change how we do things

Next steps Person-based record linkage (hospital data)

Better handling of transfers, type changes and readmissions Better understanding of cases with injury codes, but only as an additional diagnosis Might help understanding of cases with external cause code(s) but no injury code

Linkage with deaths data Better total measurement of serious and life-threatening injury

Greater use of ED and primary care data (where possible…) Better understanding of admitted cases in relation to a broader segment of all injury. Change and difference in admission fractions

External cause code validation and testing Better understanding of the reliability of external cause coding, and ways to improve it. Better understanding of cases with external cause code(s) but no injury code

Exploratory consideration of some diagnosis codes outside Chapter 19 for inclusion as ‘injury’

Potential to provide a more complete measurement and description of injury