Correspondence

We declare no competing interests.

*Björn Redfors, Yangzhen Shao, Elmir Omerovic [email protected] Department of Molecular and Clinical Medicine, Institute of Medicine, Gothenburg, Sweden (BR, YS, EO); and Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden (BR) 1

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Chung S-C, Gedeborg R, Nicholas O, et al. Acute myocardial infarction: a comparison of shortterm survival in national outcome registries in Sweden and the UK. Lancet 2014; 383: 1305–12. Mackenbach JP, Cavelaars AE, Kunst AE, Groenhof F. Socioeconomic inequalities in cardiovascular disease mortality; an international study. Eur Heart J 2000; 21: 1141–51. Marmot M, Allen J, Bell R, Bloomer E, Goldblatt P. WHO European review of social determinants of health and the health divide. Lancet 2012; 380: 1011–29. Hales S, Howden-Chapman P, Salmond C, Woodward A, Mackenbach J. National infant mortality rates in relation to gross national product and distribution of income. Lancet 1999; 354: 2047.

that lives could have been saved if the Swedish pattern of care had been replicated in the UK is misguided. The apparent difference in 30-day mortality between the UK and Sweden might be due to case ascertainment rates,2,3 or data collection practices.3,4 The media coverage5 that followed the publication of the Article1 attributed apparent excess deaths to deficiencies in NHS care and was unfair. As academics and members of the Steering Group of the Myocardial Ischaemia National Audit Project (MINAP)—the source of the UK data for that Article1—we feel a duty to bring our concerns about the interpretation of this work to the attention of The Lancet readers. We have published additional detail elsewhere.6 The views expressed are the authors’ and not those of their respective institutions. ENL, LG, and CW are employed by University College London (UCL) and work within the National Institute for Cardiovascular Outcomes Research (NICOR). ENL, LG, TQ, and CW are members of the Steering Group of the Myocardial Ischaemia National Audit Project at NICOR. Some of the authors of the paper1 on which we comment are also UCL employees and members of NICOR, and will appraise ENL, LG, and CW.

*Emmanuel N Lazaridis, Lucia Gavalova, Simon Jones, Tom Quinn, Clive Weston [email protected] University College London, London WC1E 6BT, UK (ENL, LG); University of Surrey, Guildford, UK (SJ, TQ); and Swansea University, Swansea, UK (CW) 1

Sheng-Chia Chung and colleagues1 compared 30-day mortality following admission with acute coronary syndrome to hospitals in either Sweden or England and Wales. We do not agree with the interpretation of the analyses. Although the authors explain the difference in mortality rates between the two national registries in terms of casemix and treatment factors, the confidence intervals around their estimates indicate no evidence that this difference arises from differential percutaneous coronary intervention and β blockers use, and that most of the difference cannot be explained by the combination of treatment factors considered. Thus, the message www.thelancet.com Vol 384 July 26, 2014

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Chung S-C, Gedeborg R, Nicholas O, et al. Acute myocardial infarction: a comparison of shortterm survival in national outcome registries in Sweden and the UK. Lancet 2014; 383: 1305–12. Herrett, E, Shah AD, Boggon R, et al. Completeness and diagnostic validity of recording acute myocardial infarction events in primary care, hospital care, disease registry, and national mortality records: cohort study. BMJ 2013; 346: f2350. SWEDEHEART. Annual report 2012. http://www. ucr.uu.se/swedeheart/index.php/arsrapporter/ doc_download/254-swedeheart-annual-report2012-english (accessed July 14, 2014). Gavalova L, Weston C, Birkhead J, et al. Myocardial Ischaemia National Audit Project (MINAP): How the NHS cares for patients with heart attack. Tenth Public Report 2011. http://www.hqip.org. uk/assets/NCAPOP-Library/MINAP-publicreport-2011.pdf (accessed July 14, 2014). BBC. UK heart-attack survival rate ‘should have been better’. 23 January 2014. http://www. bbc.co.uk/news/health-25841930 (accessed July 14, 2014). Lazaridis EN, Gavalova L, Jones S, et al. The UK vs Sweden: Is the NHS really so bad? PeerJ PrePrints 2014; 2: e253v1.

Authors’reply We thank the correspondents for their comments on our Article. 1 We agree with Johan Ejerhed and colleagues that understanding selection biases is vital for interpretation and we have previously shown that MINAP, like SWEDEHEART, does not capture all myocardial infarctions identified in hospital discharge data or in primary care. 2 These missing patients are likely to be sicker; it is plausible that a higher proportion of patients are missed in the UK than in Sweden and this could mean that the true mortality differences between countries are even greater. Further research is required using multiple national sources of data including primary care.3 Our paper1 does offer a guide to the clinician—clinicians have a responsibility to improve the quality, completeness, and comparability of clinical data and to address the slow diffusion of new technologies in the UK. Peter Kavsak suggests widening comparisons to include US populations; we have begun this and noted surprising international differences in clinical management of non ST-segment elevation myocardial infarction (NSTEMI). 4 We have done new analyses and can confirm that the decreases in troponin in patients with NSTEMI are associated with lower mortality (figure, appendix). The decreasing troponin is consistent with improvements in care leading to smaller infarcts and better outcomes. We agree that socioeconomic status is associated with risk of acute myocardial infarction, 5 as Björn Redfors and colleagues suggest. However, wider income inequalities in the UK compared with Sweden are unlikely to explain our results because such inequalities have remained fairly constant during most of the study period,6 and also because our analysis of CALIBER data2 (based on 16 239 patients with myocardial

James Cavallini/Science Photo Library

to explain the observed difference in short-term outcome after acute myocardial infarction.1 Previous studies2–4 have established a relation between health outcome (including cardiovascular disease) and socioeconomic inequality. Because socioeconomic inequalities are greater in the UK than in Sweden, they could explain Chung and colleagues’ findings. 1 Future studies should include socioeconomic variables in their statistical models.

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