A cross-sectional survey of Australian and New Zealand ......for an Australian or New Zealand participant (Box 1). The primary question asked respondents which of six triage methods

Critical Care and Resuscitation • Volume 19 Number 3 • September 2017

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Triage protocols have been developed to allocate critical care resources in a major infl uenza pandemic, when the volume of patients needing critical care is expected to exceed the capacity of available resources.1-4 These protocols typically select or exclude patients on the basis of illness severity, associated medical comorbidities or predicted mortality, and have been shown to increase intensive care unit bed availability in a simulated infl uenza pandemic setting.5

An ethical challenge with triage protocols is that the use of triage criteria to exclude certain patients from access to medical resources may violate the principle of justice. This is because patients who, in ethical terms, are similar due to their medical conditions having similar predicted outcomes, are treated differently.6-8 In a major disaster, when medical resources are overwhelmed, the justifi cation for using triage protocols is predicated on a principle that giving priority to the common good of the community supersedes individual autonomy.6

Decisions relating to resource allocation in many health care systems are a reality. However, a fair process is required to establish the legitimacy of such decisions.9,10 If the public perceives that the process of setting priorities in a public health emergency is unfair, they may challenge the legitimacy of the response and may not comply with restrictive measures.6 Lack of trust, and public outrage at the lack of fairness, in such processes have been problematic in the past.11-13 Few studies have examined whether the public fi nd the use of triage protocols acceptable.14

Our objective was to determine public opinion on how ICU beds should be allocated in an infl uenza pandemic. Our secondary objective was to determine public perception of fairness for the different methods that could be used to allocate ICU beds.

Methods

Study design

This binational study was a postal survey using a self-completed, written questionnaire. The sampling frame was a random selection of 2000 registered voters taken from

A cross-sectional survey of Australian and New Zealand public opinion on methods to triage intensive care patients in an infl uenza pandemic

Winston Cheung, John Myburgh, Shay McGuinness, Debra Chalmers, Rachael Parke, Fiona Blyth, Ian Seppelt, Michael Parr, Claire Hooker, Nikki Blackwell, Shannon DeMonte, Kalpesh Gandhi, Mark Kol, Ian Kerridge,

Priya Nair, Nicholas M Saunders, Manoj K Saxena, Govindasamy Thanakrishnan and Vasi Naganathan on behalf of the Infl uenza Pandemic ICU Triage 3 study investigators and the Australian and

New Zealand Intensive Care Society Clinical Trials Group

ABSTRACT

Background and objective: An infl uenza pandemic has the potential to overwhelm intensive care resources, but the views of the general public on how resources should be allocated in such a scenario were unknown. We aimed to determine Australian and New Zealand public opinion on how intensive care unit beds should be allocated during an infl uenza pandemic.Design, setting, and participants: A postal questionnaire was sent to 4000 randomly selected registered voters; 2000 people each from the Australian Electoral Commission and New Zealand Electoral Commission rolls.Main outcome measure: The respondents’ preferred method to triage ICU patients in an infl uenza pandemic. Respondents chose from six methods: use a “fi rst in, fi rst served” approach; allow a senior doctor to decide; use pre-determined health department criteria; use random selection; use the patient’s ability to pay; use the importance of the patient to decide. Respondents also rated each of the triage methods for fairness.Results: Australian respondents preferred that patients be triaged to the ICU either by a senior doctor (43.2%) or by pre-determined health department criteria (38.7%). New Zealand respondents preferred that triage be performed by a senior doctor (45.9%). Respondents from both countries perceived triage by a senior doctor and by pre-determined health department criteria to be fair, and the other four methods of triage to be unfair.Conclusion: In an infl uenza pandemic, when ICU resources would be overwhelmed, survey respondents preferred that ICU triage be performed by a senior doctor, but also perceived the use of pre-determined triage criteria to be fair.

Crit Care Resusc 2017; 19; 254-265

the Australian Electoral Commission (AEC) electoral roll,

and 2000 registered voters taken from the New Zealand

Electoral Commission (NZEC) electoral roll. The AEC and

NZEC databases were chosen because they provided the


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most pragmatic and generalisable representation of the adult population in Australia and New Zealand.15,16

Approval to conduct the study was obtained from the Sydney Local Health District Human Research Ethics Committee (CH62/6/2013-205) and the Auckland District Health Board Research Review Committee (6271). Permission was granted to access the electoral rolls in accordance with local legislation. The study was coordinated from Concord Repatriation General Hospital in Australia and Auckland City Hospital in New Zealand.

Questionnaire

A specifi c high-fi delity questionnaire was developed for the study and is shown in the Appendix (online at cicm.org.au/Resources/Publications/Journal). Participants were sent a pre-notifi cation letter 4 weeks before the questionnaire was posted. No incentives were offered to participants. Questionnaires were returned using a reply-paid envelope.

The six-page questionnaire contained a scenario adapted for an Australian or New Zealand participant (Box 1). The

primary question asked respondents which of six triage methods they preferred (Box 2) and required a single multiple choice answer. The six secondary questions asked respondents to rate each of the triage methods for fairness using a horizontal, seven-point, category rating scale with qualifi ers.17-19 Three additional questions using the same rating scale asked respondents to rate for fairness the use of age, predicted mortality and chronic comorbidity as selection criteria. Respondents could also provide their own comment using optional free text.

To mitigate order bias, participants were randomly allocated one of 12 versions of the questionnaire with the order of the six triage methods and secondary questions randomised so that they appeared fi rst and last in the same proportions.

The questionnaire was refi ned after pilot testing with consenting volunteers. To mitigate participant distress associated with receiving the questionnaire, an initial batch of 200 questionnaires was sent in both countries to determine safety. The returns over 4 weeks were reviewed

Box 1. Infl uenza pandemic scenario used in questionnaire (Australian version)


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and approved by an independent safety monitor before the remaining 1800 questionnaires were posted. All returned questionnaires were included in the fi nal analysis.

In Australia, the AEC does not allow personal information to be retained, for privacy reasons, so participants were not contacted to follow up for non-completion. Only questionnaires returned within 10 weeks after being sent were included in the study. In New Zealand, the NZEC allowed participant-identifying information to be kept, and reminder questionnaires were sent to non-completing participants after 8 weeks. An additional 6 weeks was allowed for these returning questionnaires to be included in the study. To avoid potential contamination, the 4-week safety phase and main 10-week study period ran concurrently in both countries, between October 2015 and February 2016.

Statistical analysis

The response rate was defi ned as the number of questionnaires returned divided by the number of questionnaires sent.20 Our literature review of studies using the AEC electoral roll for mail-out surveys found that the best response rate was 21%.21 Assuming that the least popular answer was chosen by 5% of the respondents, it was estimated that 1800 questionnaires would need to be sent to obtain a 95% confi dence interval (CI) of ± 10% for the least popular answer. Rounding up, we set the mail-out size at 2000.

Expected population fi gures were derived from Australian Bureau of Statistics data from June 2015 and New Zealand Census data from 2013.22-25 In a planned analysis, 95% CIs were calculated for the primary question.

Box 2. Methods used in questionnaire to triage ICU patients (Australian version)


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We use histograms, means, standard deviations, medians and interquartile ranges to describe the secondary answers. Analysis was performed by an independent statistician using Excel 2010 (Microsoft).

Results

The response rate in the main 10-week study period was 15.1% (301 replies) in Australia and 18.0% (359 replies) in New Zealand. In New Zealand, a further 181 replies were received in the 6 weeks after the reminder questionnaire mail-out for non-completing participants, giving a fi nal response rate in New Zealand of 27.0%.

The residing state, territory or province of respondents is shown in Figure 1, with expected population fi gures. The age of respondents is shown in Figure 2, with expected population fi gures.

The proportion of male respondents was 44.4% (132 respondents) in Australia and 42.7% (228 respondents) in New Zealand. The population proportion of men in Australia was 49.3% and 48.5% in New Zealand.24,25

The preferred method chosen by respondents to triage patients to the ICU in a major infl uenza pandemic is shown in Figure 3. Allowing a senior doctor to decide was the most preferred method (43.2%; 95% CI, 37.5%–48.8%) among Australian respondents, but the next most preferred method of using triage criteria predetermined by the Health Department to decide (38.7%; 95% CI, 33.1%–44.3%) was not statistically different.

Among New Zealand respondents, the most preferred method was to allow a senior doctor to decide (45.9%; 95% CI, 41.7%–50.2%). This was statistically higher than the second most preferred method of using triage criteria predetermined by a Health Department to decide (33.1%; 95% CI, 29.1%–37.1%).

Respondents’ perceptions of fairness for each of the six methods that could be used to triage ICU patients in a major infl uenza pandemic are shown in Figure 4. Respondents in both countries considered that both allowing a senior doctor to decide (Figure 4B) and using triage criteria predetermined by a Health Department (Figure 4C) to decide were fair (rated as greater than four on the rating scale). A large

Figure 1. Proportions and numbers of questionnaire responses, by state, territory or province of respondent, and by actual population proportions

22

23


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24

25

Figure 2. Age of questionnaire respondents, and actual age distribution of the population

Figure 3. Respondent preferences for questionnaire, question 1: “Which of the 6 methods do you think is the best way to decide which patients get to be transferred to the intensive care unit (ICU) in a major infl uenza pandemic disaster, when there are not enough resources to treat everyone? (Choose only 1 option)”


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Figure 4. Respondent views on fairness for methods listed in questionnaire to triage of intensive care unit (ICU) patients during an infl uenza pandemic; questions 2, 3 and 4


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Figure 4 (continued). Respondent views on fairness for methods listed in questionnaire to triage of intensive care unit (ICU) patients during an infl uenza pandemic; questions 5, 6 and 7


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proportion of respondents considered that triage decisions based on a “fi rst come, fi rst served” method (Figure 4A), random selection (Figure 4D), ability to pay (Figure 4E), or a person’s importance (Figure 4F), were unfair (rated as less than four on the rating scale).

Respondents’ perceptions of fairness for three additional selection criteria that could be used to triage patients in a major infl uenza pandemic are shown in Figure 5. Most respondents in both countries considered using a person’s chance of survival (Figure 5B) as a basis for triage decisions to be fair. A smaller majority of respondents in both countries also considered treating younger people ahead of older people (Figure 5A) and on the basis of chronic comorbidity (Figure 5C) to be fair.

Free-text comments regarding the use of age as a selection criterion refl ected that this distinction diminished as the age gap narrowed. Some comments from older respondents were critical of modern medicine prolonging life unnecessarily. Some older respondents indicated that they had lived fulfi lling lives, and that they would be happy for a younger person to take their place in the ICU in such a scenario.

Comments suggested that respondents in New Zealand were more trusting of senior doctors and less trusting of government and health departments to look after their best interests in a pandemic scenario. However, respondents who favoured the use of pre-determined criteria ahead of allowing senior doctors to triage cited several reasons. One reason was that placing the burden of decision making in such a diffi cult circumstance on one or several individuals would be unfair and potentially psychologically traumatic to those individuals. A second reason was that potential bias, prejudice or nepotism could occur if individuals made decisions based on sole discretion. A third reason was that pre-determined selection criteria were more transparent and accountable if they were ever to be legally contested.

Discussion

Our binational survey addressed one of the ethical challenges that would present if an infl uenza pandemic disaster were to occur and the demand for intensive care resources signifi cantly exceeded capacity, in Australia and New Zealand. This study showed that in Australia, most respondents preferred that triage to an ICU in a pandemic scenario be performed by either a senior doctor or by using pre-determined health department criteria. In New Zealand, triage by a senior doctor was the most preferred method. Most respondents in both countries considered both these methods to be fair overall, and perceived the other four triage methods as being unfair.

The reason for the difference between Australia and New Zealand is unknown. Both countries have predominantly

universal-access public health care systems, but Australia has a larger coexisting user-pays system. Recent political history in both countries, and comments from the survey, suggest that there may be differences in the trust that the public have in government.

The major benefi t of allowing senior doctors to allocate resources using sole discretion, during a resourcing crisis, is the ability to quickly respond to constantly changing supply and demand. However, potential problems with accountability and perception of bias remain using this method. Given that respondents in this study perceived the use of triage criteria also to be fair, we propose that, during an infl uenza pandemic, when resources are overwhelmed, ICU triage should be performed using pre-determined criteria to provide a basic framework, with a senior doctor making the fi nal decisions. We propose that this method is acceptable to the general public and provides a degree of transparency and accountability.

The questionnaire contained three questions to specifi cally gauge the public’s view on the use of age, predicted mortality and chronic comorbidity as selection criteria, because these criteria are used in current ICU triage protocols.1-3 As respondents considered all three criteria as being fair, we propose that it is reasonable to continue the use of these criteria in such protocols.

There are no large cross-sectional studies surveying the views of the general public on methods to triage ICU patients in an infl uenza pandemic. A small Massachusetts study used focus groups involving 30 members of the public to obtain opinions on scenarios related to pandemic planning.14 These consumers were strongly opposed to any model of limiting critical care.

Strengths and limitations

The limitation of our study is non-response bias due to the small sample size and low response rate. A low response rate was expected, based on results of previous studies, the variable willingness of the general public to complete written questionnaires, and the large geographical spread of the populations.21,26 Many of the randomly selected, invited participants lived in rural areas with limited access to postal services. Privacy concerns by the AEC prevented follow-up questionnaires being sent in Australia to non-responders. In New Zealand, sending a second questionnaire to non-responders improved the response rate by 50%, but the overall response rate remained low, although consistent with similar studies.

Our study used strategies to mitigate bias and to maximise the generalisability of the results. We performed an extensive literature search and consulted design experts to determine the optimal questionnaire design, specifi cally


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Figure 5. Respondent views on fairness for methods listed in questionnaire on triage of intensive care unit (ICU) patients during an infl uenza pandemic; questions 8, 9 and 10


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using a horizontal, seven-point rating scale with qualifi ers, that provides the most accurate results.18,19 The use of qualifi ers, such as “neither unfair or fair” resulted in anchoring effects, especially as seen in Figures 4A and 4D, but these effects did not signifi cantly infl uence the fi nal interpretation.

Order bias was mitigated by the use of different versions of the study questionnaires with the order of the six triage methods and secondary questions randomised. The questionnaire was extensively tested and potential harm was minimised with the use of an initial safety-phase mail out. Attempts to improve the response rate were made through the use of pre-notifi cation letters, reply-paid envelopes, minimising questionnaire content and the use of design experts to improve the questionnaire’s attractiveness.

The sampling frame was representative of the general adult population in both Australia and New Zealand, because registration on the electoral roll is compulsory. The geographical spread of respondents was consistent with the expected populations, but the higher proportions of women and older respondents in both countries may be a potential source of bias. The reason for this observation is not known, but the age bias was observed in a previous study using the AEC database.21 The study did not sample people aged under 18 years of age, nor those not enrolled on the electoral rolls, so our results cannot be generalised to these groups.

During the study’s conception, other potential sampling frames were considered, such as internet and telephone databases, but these were discounted due to their lack of generalisability to the overall adult populations of both countries, as well as cost. Internet databases had the potential to generate a large sample size, but were not well established in both countries, and were potentially biased by respondents being fi nancially remunerated, or belonging to specifi c niche consumer groups.

A comprehensive ethical discussion on triage is beyond the scope of this article. Our study did not invite the public to make an ethical judgment, nor does it offer an ethical analysis of the choices presented in the survey. We merely asked respondents to choose between six different methods of triage, all of which could be said to have a reasonable ethical basis, and to rate these for a single ethical criterion of fairness.

We conducted our study in two developed countries with universal-access public health care systems. Future studies should survey public opinion in other countries, particularly those with user-pays or resource-limited health care systems. The views and needs of disadvantaged groups, such as indigenous populations, were not examined in this study, but should be addressed in future studies, as these groups are likely to be disproportionately affected by

infl uenza pandemics, and may lack trust in senior doctors, health policy makers and the ethical judgments of the mainstream public.27,8 Future studies should refi ne triage methods by generating robust data on short-term and long-term mortality and on functional outcomes. Future studies should also examine how triage should be performed for critically ill children.

Conclusion

In Australia, respondents preferred to allow either a senior doctor or pre-determined health department criteria to triage ICU patients in an infl uenza pandemic, but in New Zealand, more respondents preferred a senior doctor to decide. Respondents in both countries considered both these methods to be fair, and also considered it fair to base triage criteria on age, chance of survival, and chronic comorbidity.

Author contributions

Winston Cheung and John Myburgh designed the study. Winston

Cheung coordinated the study in Australia. Shay McGuinness

coordinated the study in New Zealand. Winston Cheung and

Rachael Parke collated the data. Winston Cheung analysed and

interpreted the data. Winston Cheung, John Myburgh and Vasi

Naganathan drafted the manuscript. All authors had access

to the datasets, contributed to the writing and review of the

manuscript, and approved the final version.

Acknowledgements

We thank Jennifer Peat, Helen Wong, Tim Lambert (Concord

Repatriation General Hospital, Sydney, Australia); Mario D’Souza

(Sydney Local Health District, Sydney, Australia); and Eileen

Gilder, Stephnie Long, Keri-Anne Cowdrey, Jane Dalton, Aimee

Blakemore, Magda Butler (Cardiovascular ICU Research, Auckland

City Hospital, Auckland, New Zealand) for their help with our

study. We thank especially Lillian Hou for the questionnaire

graphic design, and the volunteers who helped with the

development of the questionnaire.

Competing interests

Shay McGuinness and Rachael Parke received competitive

research grants from The A+ Charitable Trust. All other authors

declare no conflicts of interest.

The New Zealand arm of this study was supported by the

A+ Charitable Trust. The study sponsor had no role in the

study’s design, conduct, data collection, data analysis, data

interpretation, manuscript preparation or the decision to submit

it for publication.


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Author detailsWinston Cheung, Intensivist,1 Clinical Associate Professor2 and

Honorary Senior Fellow3

John Myburgh, Director,3 Professor of Critical Care Medicine4

and Intensivist5

Shay McGuinness, Intensivist and Director of Research,6

Honorary Specialist7 and Adjunct Senior Research Fellow8

Debra Chalmers, Intensivist9 and Fellow6

Rachael Parke, Nurse Senior Research Fellow,6 Honorary Senior

Medical Research Fellow,7 Adjunct Senior Research Fellow8 and

Senior Lecturer10

Fiona Blyth, Professor2

Ian Seppelt, Intensivist,11 Associate Professor12,13 and Honorary

Senior Fellow3

Michael Parr, Professor,4 Director14 and Intensivist14

Claire Hooker, Senior Lecturer15

Nikki Blackwell, Intensivist,16 Associate Professor17 and Medical

Consultant18

Shannon DeMonte, Quality and Safety Clinical Nurse16

Kalpesh Gandhi, Intensivist19

Mark Kol, Director,1 Intensivist1 and Clinical Senior Lecturer2

Ian Kerridge, Professor15

Priya Nair, Director,20 Intensivist,20 Honorary Senior Fellow3 and

Conjoint Senior Lecturer4

Nicholas M Saunders, Anaesthetist21

Manoj K Saxena, Intensivist,5 Research Fellow3 and Conjoint

Lecturer4

Govindasamy Thanakrishnan, Intensivist1

Vasi Naganathan, Associate Professor2,22 and Consultant

Geriatrician23

on behalf of the Influenza Pandemic ICU Triage 3 study

investigators and the Australian and New Zealand Intensive Care

Society Clinical Trials Group

1 Intensive Care Unit, Concord Repatriation General Hospital,

Sydney, NSW, Australia.

2 Sydney Medical School, Concord, University of Sydney, Sydney,

NSW, Australia.

3 Critical Care and Trauma Division, The George Institute for

Global Health, Sydney, NSW, Australia.

4 University of New South Wales, Sydney, NSW, Australia.

5 Department of Intensive Care Medicine, St. George Hospital,

Sydney, NSW, Australia.

6 Cardiothoracic and Vascular Intensive Care Unit, Auckland

City Hospital, Auckland, New Zealand.

7 Medical Research Institute of New Zealand, Wellington, New

Zealand.

8 Australian and New Zealand Intensive Care Research Centre,

Monash University, Melbourne, VIC, Australia.

9 Intensive Care Unit, Hawke’s Bay Fallen Soldiers’ Memorial

Hospital, Hastings, New Zealand.

10 University of Auckland, Auckland, New Zealand.

11 Department of Intensive Care, Nepean Hospital, Sydney,

NSW, Australia.

12 Australian School of Advanced Medicine, Macquarie

University, Sydney, NSW, Australia.

13 Sydney Medical School, University of Sydney, Sydney, NSW,

Australia.

14 Department of Intensive Care, Liverpool Hospital, Sydney,

NSW, Australia.

15 Centre for Values, Ethics and the Law in Medicine, University

of Sydney, Sydney, NSW, Australia.

16 Prince Charles Hospital, Brisbane, QLD, Australia.

17 University of Queensland, Brisbane, QLD, Australia.

18 The Alliance for International Medical Action, Dakar, Senegal.

19 Department of Intensive Care, Blacktown Hospital, Sydney,

NSW, Australia.

20 St. Vincent’s Hospital, Sydney, NSW, Australia.

21 Norfolk and Norwich University Hospital National Health

Service Foundation Trust, Norfolk, United Kingdom.

22 Centre for Education and Research on Ageing, University of

Sydney, Sydney, NSW, Australia.

23 Ageing and Alzheimers Institute, Concord Repatriation

General Hospital, Sydney, NSW, Australia.

Correspondence: [email protected]

References1 Christian MD, Hawryluck L, Wax RS, et al. Development of a

triage protocol for critical care during an influenza pandemic. CMAJ 2006; 175: 1377-81.

2 Hick JL, O’Laughlin DT. Concept of operations for triage of mechanical ventilation in an epidemic. Acad Emerg Med 2006; 13: 223-229.

3 New South Wales Ministry of Health. Influenza pandemic — providing critical care [policy directive]. PD2010_028. Sydney: NSW Health, 2010. http://www1.health.nsw.gov.au/PDS/pages/doc.aspx?dn=PD2010_028 (accessed Jun 2017).

4 Cheung W, Myburgh J, Seppelt IM, et al. Development and evaluation of an influenza pandemic ICU triage protocol. Crit Care Resusc 2012; 14: 185-90.

5 Cheung W, Myburgh J, Seppelt IM, et al. A multicentre evaluation of two intensive care unit triage protocols for use in an influenza pandemic. Med J Aust 2012; 197: 178-81.

6 Sztajnkrycer MD, Madsen BE, Baez AA. Unstable ethical plateaus and disaster triage. Emerg Med Clin North Am 2006; 24: 749-68.

7 White DB, Katz MH, Luce JM, Lo B. Who should receive life support during a public health emergency? Using ethical principles to improve allocation decisions. Ann Intern Med 2009; 150: 132-8.

8 Kaposy C. Accounting for vulnerability to illness and social disadvantage in pandemic critical care triage. J Clin Ethics 2010; 21: 23-9.

9 Thompson AK, Faith K, Gibson JL, Upshur REG. pandemic influenza preparedness: an ethical framework to guide decision-making. BMC Medical Ethics 2006; 7: 12.

10 Daniels N. Accountability for reasonableness. BMJ 2000; 321: 1300-1.

11 Slovic P. The perception of risk. New York: Earthscan Publications, 1999.


ORIGINAL ARTICLES

265

12 Selgelid MJ, Battin MP, Smith CB. Ethics and infectious disease. Oxford: Wiley-Blackwell, 2006.

13 Glik DC. Risk communication for public health emergencies. Annu Rev Public Health 2007; 28: 33-54.

14 Levin D, Cadigan RO, et al. Altered standards of care during an influenza pandemic: identifying ethical, legal, and practical principles to guide decision making. Disaster Med Public Health Prep 2009; 3: S132-S140.

15 Smith W, Mitchell P, Attebo K, Leeder S. Selection bias from sampling frames: telephone directory and electoral roll compared with door-to-door population census: results from the Blue Mountains eye study. Aust N Z J Public Health 1997; 21: 127-33.

16 O’Toole J, Rodrigo S, Sinclair M, Leder K. The Australian Electoral Commission roll has good utility for ‘niche’ household recruitment in population health studies. Aust N Z J Public Health 2009; 33: 137-9.

17 Hyland ME, Sodergren SC. Development of a new type of global quality of life scale, and comparison of performance and preference for 12 global scales. Qual Life Res 1996; 5: 469-80.

18 Jaeschke R, Singer J, Guyatt GH. A comparison of seven-point and visual analogue scales. Controlled Clin Trials 1990; 11: 43-51.

19 Paul-Dauphin A, Guillemin F, Virion J-M, Briancon S. Bias and precision in visual analogue scales: a randomised controlled trial. Am J Epidemiol 1999; 150: 1117-27.

20 American Association for Public Opinion Research. Standard definitions: final dispositions of case codes and outcome rates for surveys (8th edition, 2015). http://www.aapor.org/Publications-Media/AAPOR-Journals/Standard-Definitions.aspx (accessed Jun 2017).

21 Bellamy N, Wilson C, Hendrikz J. Population-based normative values for the Western Ontario and McMaster (WOMAC) osteoarthritis index: part I. Semin Arthritis Rheum 2011; 41: 139-48.

22 Australian Bureau of Statistics. Australian demographic statistics. June quarter, 2015. Canberra: ABS, 2015. http://www.ausstats.abs.gov.au/ausstats/subscriber.nsf/0/801757AC98D5DE8FCA257F1D00142620/$File/31010_jun%202015.pdf (accessed Jun 2017).

23 Statistics New Zealand. 2013 Census QuickStats about a place. Wellington: Statistics NZ, 2013. http://www.stats.govt.nz/Census/2013-census/profile-and-summary-reports/quickstats-about-a-place.aspx (accessed Jun 2017).

24 Australian Bureau of Statistics. Australian demographic statistics, June Quarter 2015. Time series spreadsheets, Table 59: Estimated resident population by single year of age, Australia. Canberra: ABS, 2015. http://www.abs.gov.au/AUSSTATS/[email protected]/DetailsPage/3101.0Jun%202015?OpenDocument (accessed Jun 2017).

25 Statistics New Zealand. Infoshare population estimates — DPE. Estimated resident population by age and sex (1991+). Wellington: Statistics NZ, 2013. http://www.stats.govt.nz/infoshare (accessed Jun 2017).

26 Glass DC, Kelsall HL, Slegers C, et al. A telephone survey of factors affecting willingness to participate in health research surveys. BMC Public Health 2015; 15: 1017.

27 The Australian and New Zealand Intensive Care Society influenza investigators. Critical care services and 2009 H1N1 influenza in Australia and New Zealand. N Engl J Med 2009; 361: 1925-34. ❏

Documents

A cross-sectional survey of Australian and New Zealand ......for an Australian or New Zealand participant (Box 1). The primary question asked respondents which of six triage methods