Editorials Ecological studies: financial responsibility for patients. The first The need for reform ADDRESS FOR CORRESPONDENCE use with caution example is in the UK where groups of GPs Primary care in many countries is Martin Roland (clinical commissioning groups) now have unrecognisable from 20 years ago. Institute of Public Health, Forvie Site, University of budgetary responsibility for the majority Countries are bound to continue to reform Cambridge School of Clinical Medicine, Box 113 of the healthcare budget to their patients their healthcare systems to deal with the Cambridge Biomedical Campus, Cambridge, including hospital and specialist care. The new challenges of ageing populations, and CB2 0SR, UK Background second example is in the US where the therefore changes to both the organisation E-mail: [email protected] Ongoing debates about the quality of NHS concept of ‘accountable care organisations’ and financing of primary care are inevitable. organisations have made ecological studies “Ecological studies in health services research are gives budgetary responsibility for defined GPs have proved to be both adaptable and REFERENCES fashionable. One such study in the UK a powerful tool and with the wealth of organisational populations to providers of health care, entrepreneurial over many years. They will 1. Kringos D, Boerma W, Bourgueil Y,et al. considered the association between the The strength of primary care in Europe: an level data now available there are increasing numbers although in the US this is more likely to be need to show continued ability to adapt to a international comparative study. Br J Gen Pract average clinical quality of primary care a combination of generalists and specialists changing environment. 2013; DOI: 10.3399/bjgp13X674422. provided by primary care trusts and the of research questions where they are the study rather than primary care physicians having 2. Schoen C, Osborn R, Squires D,et al. A survey trusts’ rate of admission for coronary heart design of choice.” lead responsibility. Martin Roland, of primary care doctors in ten countries shows disease.1 An alternative to this ecological An anomaly of the UK’s current RAND Professor of Health Services Research, progress in use of health information technology, approach, which used data aggregated to Institute of Public Health, University of Cambridge less in other areas. Health Affairs 2012; 31(12): healthcare reform is that the CCGs are School of Clinical Medicine, Cambridge. 2805–2816. the level of a primary care trust, would responsible for purchasing specialist care have been to have used data for individual public3 the amount of data available is only epidemiological research also apply to 3. Kringos D, Boerma W, van der Zee J, but do not have responsibility for primary patients, and to have asked if there was an going to increase. ecological studies, for example in relation Ellen Nolte, Groenewegen P. Europe’s strong primary care care. It seems clear that they cannot systems are linked to better population health One strong advantage of using publicly to potential confounding (where two Director, Health and Healthcare, RAND Europe, association between the clinical quality of but also to higher health spending.Health Affairs manage a population budget without taking Cambridge. care an individual receives and their own available data in research is that there are domains of care appear associated, but an interest in both, and early indications 2013; 32(4): 686–694. chance of being hospitalised for coronary no problems with data confidentiality. When this is in fact simply because they are are that they are doing exactly that with, for 4. Starfield B, Shi L, Macinko J. Contribution of heart disease. By using aggregated data looking at associations between risk factors both associated with a third, confounding, Provenance primary care to health systems and health. example, contracts that involve specialist, Commissioned; not externally peer reviewed. Milbank Q 2005; 83(3): 457–502. in ecological studies the relationship for and outcomes, linking information about variable). Where there is confounding by 14 primary, and community care. Currently 5. Friedberg MW, Hussey P, Schneider E. Primary individual patients is not directly explored, individual patients often requires extensive individual level variables (such as clinical neither hospital nor general practice Competing interests care: a critical review of the evidence on quality although individual relationships may often ethical and governance approval. Linking diagnosis or disease severity case mix payment systems in the UK encourage The authors have declared no competing interests. and costs of health care.Health Affairs 2010; (correctly or incorrectly) be inferred from data at the organisational level, however, or sociodemographic variation), then if integrated care, and both need to change 29(5): 766–772. population-based analyses. Ecological does not, as usually the data have been individual level data are available for one to do so. DOI: 10.3399/bjgp14X676960 6. Vedsted P, Olesen F. Are the serious problems studies can either be descriptive, for published and are in the public domain of the measures of interest, accounting in cancer survival partly rooted in gatekeeper already. Ecological studies also allow us to for potential confounding at the ecological principles? An ecologic study. Br J Gen Pract example, exploring variation between 5 2011; DOI: 10.3399/bjgp11X588484. populations, or consider associations such look nationwide providing evidence that is level is possible. Information may also 7. Nolte E, McKee M. Variations in amenable as the example above. In health services potentially more generalisable than from be available at the organisational level mortality — trends in 16 high-income nations. research, where healthcare organisations studies considering individuals, but in only a about possible confounders, but individual Health Policy 2011; 103: 47–52. rather than individual patients are often small geographical area. A further strength level data are needed if individual level 8. Powell Davies PG, Williams AW, Larsen K,et al. the focus of inquiry, ecological studies are of ecological studies is that where data are confounders are the concern. Coordinating primary health care: an analysis of often an appealing tool. For example, a available the exploration of potential trends The importance of these last two the outcomes of a systematic review.Med J Aust 2008; 188(8 Suppl): S65–S68. recent study looking at the features of over time can be considered with relative points (potential for ecological fallacy 9. Coleman K, Mattke S, Perrault P, Wagner E. general practices associated with lower ease. and unmeasured confounding), when Untangling practice redesign from disease coronary heart disease mortality was The strength of an ecological study for interpreting correlations observed at the management: how do we best care for the more concerned with the practice at an looking at associations at the institutional organisational level, cannot be overstated. chronically ill. Ann Rev Public Health 2009; 30: organisational level than with individuals.2 level (hospital, CCG or GP practice) is A simple, unadjusted, correlation of two 385–408. balanced by the fact that we cannot draw measures at the population level has the 10. Smith J, Holder H, Edwards N,et al. Securing Strengths of this approach: the future of general practice: new models of conclusions about individual patients from potential for eye-catching headlines, such primary care. www.nuffieldtrust.org.uk/sites/ Open data and organisation population data. We can tell whether GP as the study of the association between files/nuffield/130718_securing_the_future_of_ analyses practices where patients report a better chocolate consumption and winning a general_practice-_full_report_0.pdf (accessed 13 The availability of data describing NHS experience of care are those that achieve Nobel prize.6 However, the potential for Jan 2014). organisations has never been greater. A higher QOF targets,4 but this tells us ecological studies to lead into suboptimal 11. Casalino L, Wu F, Ryan A,et al. Independent practice associations and physician-hospital large volume of UK healthcare process and nothing about the association between policy-making is high; confounding and organisations can improve care management outcome data is becoming publicly available patient experience and the quality of clinical ecological fallacy mean that an unthinking for smaller practices. Health Affairs 2013; 32: from the Health and Social Care Information care at the patient level. Ecological studies analysis of associations at the organisational 1367–1382. Centre (http://www.hscic.gov.uk/) and via are at best hypothesis generating when rather than the individual level may have 12. Charlesworth A, Davies A, Dixon J.Reforming the government open data website (http:// considering individual level associations and far reaching consequences. Recently it payment for health care in Europe to achieve care is needed to avoid the risk of ecological better value. www.nuffieldtrust.org.uk/ www.data.gov.uk/) with GP practice, has been claimed that NHS hospitals that publications/reforming-payment-health-care hospital, and clinical commissioning group fallacy: assuming the associations that operate in a more competitive geographical (accessed 13 Jan 2014). (CCG) indicators available. Indicators cover exist at the population level persist at the environment have a lower mortality rate 13. Roland M. Pay for performance: not a magic measures including population, service, individual level. Ecological analyses which for patients with myocardial infarction.7 bullet [editorial]. Ann Intern Med 2012; 157: clinical outcome, prescribing and patient consider within-institution trends-over-time Whether this association was causal or not 912–913. experience. The UK Data Archive (http:// are less vulnerable to these problems, but has been a subject of a lively debate.8 14. Naylor C, Curry N, Holder H,et al. Clinical data-archive.ac.uk/) is another source of not immune. Data completeness is also important. commissioning groups: supporting improvement in general practice. www.nuffieldtrust.org.uk/ publicly available data, including individual Complete and accurate data is incentivised publications/clinical-commissioning-groups- level data from health surveys. With the Cautions: confounding, bias, and in the NHS, but there remains variation in supporting-improvement-general-practice UK white paper from 2012 presenting the ecological fallacy quality and validity across organisations. (accessed 13 Jan 2014). government strategy to make more data Considerations applicable to any type of For example, exception reporting varies

64 British Journal of General Practice, February 2014 British Journal of General Practice, February 2014 65 Editorials Cauda equina syndrome:

ADDRESS FOR CORRESPONDENCE implications for primary care “... the potential for over-interpretation of results and Catherine Saunders Cambridge Centre for Health Services Research, generation of spurious findings is ever present.” Institute of Public Health, Forvie Site, Addenbookes Hospital, Cambridge, CB2 0SR UK. Background E-mail: [email protected] Back pain is common in primary care. A practice with a population of 10 000 patients “It is one of the major causes of litigation in the NHS, across GP practices in the UK9 and there and reporting health services research will have 610 patients (6% of the practice both for primary and secondary care.” is considerable variation in data quality in carried out using routine health data are population) consulting per year, and while hospital-acquired infection surveillance.10 clearly wider than the epidemiological poor outcomes are common (around 60% Measurement bias (where errors in concerns about the ecological study design will still suffer pain at 12 months) GPs need data measurement are associated with alone. The RECORD (the REporting of to remain vigilant and actively consider more sinister complications. Anatomy of cauda equina have a significant increase in back pain healthcare organisation performance) can studies Conducted using Observational The spinal cord terminates at L1. Below with CES. Some get relief from sitting up also be a concern even using standardised Routinely-collected Data) statement, an Cauda equina syndrome (CES) is a this emerges a ‘horse’s tail’ of rootlets (presumably because flexion of the lumbar publicly reported data. Further, where data extension of STROBE, (STrengthening nasty complication of disc herniation, and (hence its name) that supply not only the spine widens the vertebral canal). is sparse, confidentiality requirements in the Reporting of OBservational studies in sometimes, low back surgery, and rarely lower limbs, but also bladder, bowel and Intimate examinations are not always the public reporting of data means that Epidemiology) is in development, defining spinal tumours (both primary or secondary). sexual functions. A critical feature of CES practical in primary care settings, but if information is suppressed in public sources reporting guidelines for observational While this may be considered a rare is the loss of perineal sensation, unilateral perineal sensation is tested, then the sharp where it may be individually identifiable; for studies using health data routinely collected REFERENCES condition, Hospital Episode Statistics (HES) or bilateral. Loss of sensation may be first end of an unravelled paperclip is a useful example, data may be disproportionately for non-research purposes. 1. Bottle A, Gnani S, Saxena S,et al. Association data recorded 800 CES related operations between quality of primary care and 1 noticed when cleaning the perineum after tool, and better tolerated than a disposable more likely to be missing for single-handed Ecological studies in health services in England in 2010–2011. It is one of the hospitalization for coronary heart disease in voiding or defaecation. In trying to prevent needle or cotton wool. Make sure both sides GP practices. research are a powerful tool and with the major causes of litigation in the NHS, both England: national cross-sectional study. J Gen CES, it is reasonable to warn patients with are tested and results documented. wealth of organisational level data now Intern Med 2008; 23(2): 135–141. for primary and secondary care. This is not disc herniation to look out for this symptom If a rectal examination is performed, it may Further considerations: available, there are increasing numbers 2. Levene LS, Baker R, Bankart MJG, Khunti K. surprising, as a previously fit individual is and to report any disturbance of normal be misleading because tone is maintained in power and reliability of research questions where they are Association of features of primary health care rendered, in various combinations, and often urinary function. Highlighting this in any CES-I. Recent work with a model suggests Other methodological questions should also the study design of choice. However, the with coronary heart disease mortality. JAMA in perpetuity, incontinent of urine and faeces, 2010; 304(18): 2028–2034. written patient information provides a useful that most doctors are not good at assessing be considered. The statistical reliability of the potential for over-interpretation of results with loss of perineal, penile, and vaginal 3. UK Government Cabinet Office. Unleashing prompt to patients. This may precipitate degrees of anal tone, so we should not be measures in question at the organisational and generation of spurious findings is ever sensation, and major disturbance of sexual the potential. CM8353 Open Data White Paper. inappropriate attendances, but it is probably reassured that all is well if the anal tone level are important to consider.11 present. Good practice in the use of routine 2012. http://www.data.gov.uk/sites/default/files/ function. Self-catheterisation, chronic back better to err on the side of safety. As is so seems strong.4 These findings should be Additionally, if several comparisons are health data for research and the use of Open_data_White_Paper.pdf (accessed 13 Jan and leg pain are often added in to the mix.2 recorded, and these findings, positive or being made then statistical tests should standard epidemiological precautions 2014). often the case, the GP is damned if they negative, are critical for later management be adjusted for multiple testing. The are necessary when carrying out and 4. Llanwarne NR, Abel GA, Elliott MN,et al. Types of Cauda equina syndrome do and damned if they don’t warn. Other Relationship between clinical quality and risk factors are not well established. If the of the patients and of establishing your good temptation to start correlating everything interpreting these studies. There are two main types of CES: CES-R patient experience: analysis of data from the patient has already had a scan showing practice. with everything else, just because the English Quality and Outcomes Framework and and CES-I. R is for retention, where there a developmentally narrow vertebral canal, data are freely available and accessible, Catherine Saunders, the national GP Patient Survey. Ann Fam Med is established retention of urine, and I is for Research Associate — Statistician, University of then even a small disc prolapse can threaten MRI scans and CES should be avoided and analyses should be 2013;11(5): 467–472. incomplete, where there is reduced urinary Cambridge, Cambridge Centre for Health Services 5. Rowan K, Harrison D, Brady A, Black N. the cauda equina. In most cases there is a The only way to exclude the diagnosis of hypothesis-led wherever possible. Research, Institute of Public Health, Cambridge. sensation, loss of desire to void or a poor Hospitals’ star ratings and clinical outcomes: massive lumbar disc prolapse that fills a CES is get an emergency MRI scan, which Analyses also need to be adequately stream, but no established retention and ecological study. BMJ 2004; 328(7445): 924– normal sized vertebral canal, compressing may not be available to many clinicians powered. For example, given there are overflow. Both need immediate referral for Gary Abel, 925. the rootlets of the cauda equina. CES working in primary care, especially outside only around 160 hospitals in England, a urgent surgery, but CES-R is less likely to be Senior Research Associate — Statistician, University 6. Messerli FH. Chocolate consumption, cognitive can occur in people with a long history of of routine working hours. About 40% of study using all of these would have 80% of Cambridge, Cambridge Centre for Health function, and Nobel laureates. N Engl J Med reversible. In CES-I, the time window from recurrent disc prolapse when a further and requested scans show no evidence of cauda power to detect a correlation of 0.22. While Services Research, Institute of Public Health, 2012; 367(16): 1562–1564. onset of cauda equina symptoms to surgical Cambridge. larger prolapse occurs. GP’s have been equina compression. The syndrome is then this would not be described as a strong 7. Cooper Z, Gibbons S, Jones S, McGuire A. Does decompression should be <48 hours caught out by cries of despair from a patient attributed to uncontrolled back pain. Expert correlation it is larger than values often hospital competition save lives? evidence from (some say 24 hours) to have a reasonable the English NHS patient choice reforms.Econ with a long history of disc prolapse without secondary care clinicians cannot definitively found in ecological studies. The fact that Acknowledgements chance of reversal. In practice it is not as J 2011; 121(554): F228–F260. CES or with an excessive ‘out of hours’ confirm or deny a CES diagnosis without only relatively strong associations will ever We thank Dr Georgios Lyratzopoulos (Cambridge simple as this. Some slow onset cases Centre for Health Services Research) for helpful 8. Bloom N, Cooper Z, Gaynor M,et al. In defence complaint record. There is some evidence MRI, and so why should any other sort be detected by ecological studies of this of our research on competition in England’s reverse after longer delays, but from the comments and his critical review of the manuscript. that obesity is a risk factor for CES.3 The of doctor? Unfortunately the record of sample size potentially encourages the National Health Service. Lancet 2011; legal point of view, these times are widely question ‘can you feel your bottom when A&E departments is not good at spotting publication of false-positive results as any 378(9809): 2064–2065; author reply 2065–2066. accepted criteria. CES-R with retention and Provenance you wipe yourself?’ is a useful screening CES either; even when an experienced GP statistically significant finding accompanies Freely submitted; not externally peer reviewed. 9. Doran T, Fullwood C, Reeves D,et al. Exclusion overflow may not be identified for what it of patients from pay-for-performance targets that is easily incorporated into the back pain has made it clear that they suspect CES. a large effect size. Similar cautions apply is by patients and their doctors, making to ecological studies in general practice by English physicians. N Engl J Med 2008; consultation. A specific change in bladder Probably the only way to improve diagnosis Competing interests 359(3): 274–84. careful questioning and clarification of function relating to the evolution of back is to improve access to out of hours MRI settings when only a small geographical The authors have declared no competing interests. responses essential. Even if it is suspected, 10. Tanner J, Padley W, Kiernan M,et al. A and leg symptoms is another. Many patients scanning. The National Spinal Task Force area is considered (for example, within a benchmark too far: findings from a national the patient may have reached this stage via CCG). Additionally, if the measurement of DOI: 10.3399/bjgp14X676979 survey of surgical site infection surveillance.J CES-I. There may be reasonable grounds organisation performance does not have Hosp Infect 2013; 83(2): 87–91. for complaint for not spotting this process high reliability then power will be further 11. Lyratzopoulos G, Elliott MN, Barbiere JM,et al. sooner or failure to warn. It is helpful to decreased. How can health care organizations be reliably “Always be alert to cauda equina syndrome. It is not compared? Lessons from a national survey record when symptoms and signs first of patient experience. Med Care 2011; 49(8): started, as this has management and Best practice and conclusions as rare as you may think.” 724–733. medico-legal implications. The need for good practice in working with

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