Self measurement of blood pressure: a community survey - Nature

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May 3, 2007 - severe or terminal illness or individual frailty, were excluded (n= 393 (6.6%)). Starting in June 2005, questionnaires and prepaid envelopes ...
Journal of Human Hypertension (2007) 21, 741–743 & 2007 Nature Publishing Group All rights reserved 0950-9240/07 $30.00 www.nature.com/jhh

RESEARCH LETTER

Self measurement of blood pressure: a community survey Journal of Human Hypertension (2007) 21, 741–743; doi:10.1038/sj.jhh.1002217; published online 3 May 2007

New technology means that self-measurement or testing of blood pressure (BP) is potentially available for many people but few data exist on how common it is. A community survey in Birmingham, UK in June 2005 (2931 responders; response rate 54%) of self-testing of BP showed that 9% of a randomly selected population sample had selftested their own BP. Greater public awareness of BP through self-testing has the potential to improve the detection and treatment of BP but this will only be possible if professionals are aware of it. The advent of accurate automated electric sphygmomanometers means that BP measurement is no longer uniquely the preserve of trained nursing or medical staff. BP measurement has penetrated the high street with pharmacies and other public places offering the service.1 It is likely that direct marketing of electronic sphygmomanometers to the public has resulted in significant numbers of people self testing BP in the community, but other than market research, we were unable to find data regarding how common self-monitoring is in the UK. Self-monitoring has the potential to prompt behavioural changes leading to reductions in BP levels with consequent health benefits for patients and reduced levels of health care contact.2–4 It may also be a better predictor of cardiovascular events than clinic measurements.5 Two recent systematic reviews of patient self-monitoring of BP, under the recommendation and guidance of health professionals, have found that BP can be reduced, at least in the short term by around 4/2 mm Hg,2,3 with similar subsequent results from the only UK randomised controlled trial (RCT) of self-monitoring.4 However, community surveys suggest that many people with hypertension remain undiagnosed and so increased self-testing of BP could lead to increased demand for care following self-diagnosis and without informed interpretation of results, may increase anxiety.6 Where self-monitoring is concealed, it may affect the professional-patient relationship: some patients are reluctant to discuss selfcare strategies with their doctors7 and evidence from the UK RCT suggested that only around half of those in the self-monitoring arm of the study shared their BP results with their general practitioner (GP) (McManus et al., data on file).

Following ethical and RM&G approval, four general practices in Birmingham were recruited to a study that aimed to determine the extent of self-testing. People, whom the GP deemed inappropriate to approach, for example because of recent bereavement, severe or terminal illness or individual frailty, were excluded (n ¼ 393 (6.6%)). Starting in June 2005, questionnaires and prepaid envelopes were sent to 5545 people aged over 18 years selected randomly from those registered with the participating practices. The questionnaire defined self-testing as testing that was undertaken without the involvement of a doctor or a nurse. It asked whether the respondent had used a self test for BP measurement or would use such a test in the future. Respondents were also asked about 12 other specified types of self-testing (for example diabetes, cholesterol, cancer screening (bowel, prostate)). Differences between those using and not using self-tests were explored using the w2-test apart from age for which a t-test was used. Prevalence rates were directly standardised to the England population. The predictors of self-test use were investigated using forward stepwise logistic regression. One hundred and thirty-three questionnaires were returned because they were undeliverable. From the remaining 5412 people, 2925 completed questionnaires were received with a further 207 returned blank, giving a return rate of 58% and a response rate of 54%. Respondents were more likely to be women (55%) and most were of white ethnicity (92%). Two hundred and seventy-six (9% crude prevalence) reported using a BP self-test. Standardised rates of self-testing were 8.3 and 7.8% in women and men respectively. Characteristics of those measuring their own BP are shown in Table 1. The mean age of those people who had self-monitored was 58 years compared to 53 in those who had not self-monitored with peak-reported use between ages 55 and 64 years. People measuring their own BP were more likely to have a university or higher degree (26 vs 18%, Po0.01) and were more likely to be retired (40 vs 32%, Po0.05) than those who did not. They were less likely to smoke (13 vs 20%, Po0.01) than those who had not measured their own BP but more likely to have a long-term illness (37 vs 27%, Po0.001). People who had self-monitored their own BP were also more likely to have used other self-tests: for example 28/276 (10%) of those who self-tested BP also self-tested cholesterol and 68/276 (25%) had self-tested for glucose compared to 28/2649 (1%) and 157/2649 (6%) respectively of those who had not

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Table 1 Characteristics of those people reporting self-testing of blood pressure Characteristic

Have you ever used a self-test for blood pressure? Yes (n)

Yes (% of total number) Othera (n) Othera (% of total number)

Total number 276 Female 153 Male 123 Mean age, years (s.d.) 58 (15.3) White ethnicity 248 In paid full or part-time employment 125 110 Retiredc Has university or higher degree 71 Smoker 37 Takes regular exercise 134 Long-term illness 101 Health not good 42 Use of other self-test including pregnancy test 135 Use of other self-test excluding pregnancy test 104

100 55 45 — 90 45 40 26 13 49 37 15 49 38

2649 1464 1185 53 (17.7) 2450 1370 860 480 541 1246 710 282 693 320

100 55 45 — 92 52 32 18 20 47 27 11 26 12

Pb

NS o0.001 NS o0.05 o0.05 o0.01 o0.01 NS o0.001 o0.05 o0.0001 o0.0001

a

Those answering ‘no’, or where the answer was not known or left blank. w Test apart from age (t-test). c Excludes people who said they were retired but also had paid employment. b 2

self-tested for BP. Approximately half (50.2%) of all respondents reported that they would consider selftesting BP in the future. Logistic regression confirmed the significant factors predicting BP self-test use to be increasing age (Po0.0001), female gender (Po0.0001), having a university degree (Po0.05) and living in a more affluent area (Po0.05). This study has shown that almost 10% of the adult population report using a self-test for BP, without the involvement of a health professional, and that 50% would consider using a self-test in the future. Those people engaging in self-testing of BP were more likely to have self-tested for other modalities including glucose and cholesterol, were older, more likely to suffer from a chronic disease and more likely to be retired than those not monitoring. This was a postal survey with a response rate of 54% and was undertaken in one area of the country, namely Birmingham. In any survey, there is a danger that responders are different from the rest of the population and non-responders may have selfmonitored more or less frequently than responders. Comparison of the study population as a whole with census data for the West Midlands suggests that respondents were older (census 41.6%, study population 53.1%) and probably as a consequence overrepresented women (census: 51%; study: 55%) but included similar proportions of people describing themselves as having white ethnicity (census 91, study 92%). Standardised rates were therefore calculated to allow for the response bias. Data from the Quality and Outcomes Framework of the new General Practice Contract show that around 12% of the adult population have been labelled as hypertensive by their general practitioner.8 The current study did not differentiate between hypertensive and normotensive individuals and so it is not clear to what extent the selfmonitoring and hypertensive populations overlap, Journal of Human Hypertension

but studies from Europe suggest that those with hypertension, self-monitor more commonly.9,10 The results show only a slightly higher prevalence of self-monitoring than previously described in a study in the United States (Minnesota) in 1987 which is interesting given the improvements in technology and ease of measurement over the last 20 years.11 This may reflect differences between the United Kingdom and United States, or in the precise form of question asked but also reflects our intention to establish the prevalence of self-testing that had not been initiated by a health professional. In contrast to other new technologies such as basic computer skills where older people are in the lowest group of users, self-testing of BP had peak penetrance in middle-aged and older people.12 This is presumably a function of the increased prevalence of chronic disease and therefore awareness of high BP amongst older populations.6 Self-monitoring of BP has a number of potential benefits. As well as better control of BP, white coat hypertension can be detected.13 People with hypertension rate self-monitoring highly, particularly at home, in comparison with professional monitoring, and it appears from the current study that they are taking matters into their own hands.4,14 This is despite the fact that BP monitors are not available on the NHS and cost at least d40 ($95, h74) for a validated upper arm model.15 Users of self-monitoring in this survey were less likely to be in employment, mostly because they were retired, but were more likely to have received a university education. However, the use of self-monitoring without the involvement of medical or nursing staff leads to several important issues. To measure BP accurately, validated and calibrated electronic sphygmomanometers are required. Periodic calibration is rarely offered to the general public and Hahns’11 work found that a proportion of machines in use in the

Research Letter 743

community were very inaccurate. Instructions for electronic sphygmomanometers should include advice regarding calibration, method of use, diagnostic and treatment targets. To gain maximum benefit, self-testing of BP should take place within a partnership between patients and professionals. Practices could purchase machines and share them between patients, a model that has been successfully trialed.4 Patients could report home readings, which would be incorporated into the clinical record. Professional staff could be trained in the integration of self-testing into daily practice including the interpretation of multiple BP readings. In summary, this work has shown that BP selftesting without the involvement of a doctor or nurse is now undertaken by an appreciable minority of the general population. This provides a great opportunity for renewed collaboration between professionals and their patients, but further work is required to establish the most appropriate ways of achieving this. What is known about topic K Self-testing of blood pressure is rated highly by patients and can lead to reductions in blood pressure. K Other than market research, no data exist regarding the prevalence of self-testing in the community. What this study adds K 9% of a randomly selected community sample reported self-testing blood pressure without the involvement of a health professional. K Self-testing of blood pressure was most common amongst those aged 55–64 years and more common with higher educational attainment.

Acknowledgements This study was approved by Solihull LREC, 22 March 2005, Ref. 05/Q2706/13 R&D for Birmingham and Solihull PCT Consortium, Research Management and Governance Approval, 29 June 2005, Project No. 754. This work was funded by PBS Small Grant (C9783/A5037: self-test kits for cancer, prevalence of use, characteristics of users and implications of self-testing for health care services – a feasibility study). RM was funded by a National Primary Care Post Doc Award, AR by a NHS R&D Researcher Development Award and SW by a National Primary Care Clinical Scientist Award. RJ McManus1, A Ryan1, S Greenfield1, HM Pattison2, S Clifford1, J Marriott2 and S Wilson1 1 Department of Primary Care and General Practice, Primary Care Clinical Sciences Building, University of Birmingham, Edgbaston, Birmingham, UK and 2 School of Life & Health Sciences, Aston University, Aston Triangle, Birmingham, UK E-mail: [email protected] Published online 3 May 2007

References 1 Hamilton W, Round A, Goodchild R, Baker C. Do community based self-reading sphygmomanometers improve detection of hypertension? A feasibility study. J Public Health Med 2003; 25(2): 125–130. 2 Cappuccio FP, Kerry SM, Forbes L, Donald A. Blood pressure control by home monitoring: meta-analysis of randomised trials. BMJ 2004; 329: 145–151. 3 Fahey T, Schroeder K, Ebrahim S. Interventions used to improve control of blood pressure in patients with hypertension. Cochrane Database Syst Rev 2006; Issue 2: Art. No.: CD005182. doi:10.1002/14651858. CD005182.pub2. 4 McManus RJ, Mant J, Roalfe A, Oakes RA, Bryan S, Pattison HM, Hobbs FD. Targets and self monitoring in hypertension: randomised controlled trial and cost effectiveness analysis. BMJ 2005; 331: 493–499. 5 Bobrie G, Chatellier G, Genes N, Clerson P, Vaur L, Vaisse B et al. Cardiovascular prognosis of ‘‘masked hypertension’’ detected by blood pressure self-measurement in elderly treated hypertensive patients. JAMA 2004; 291(11): 1342–1349. 6 Sproston K, Primatesta P (eds). Health Survey for England 2003, volume 2. Risk Factors for Cardiovascular Disease. London: TSO, 2003, pp 188. 7 Stevenson FA, Britten N, Barry CA, Bradley CP, Barber N. Self-treatment and its discussion in medical consultations: how is medical pluralism managed in practice? Soc Sci Med 2003; 57: 513–527. 8 Quality and Outcomes Framework Information. NHS Health and Social Care Information Centre. Leeds 2006 [updated 28 9 2006; cited 24th April 2007]. Available from: http://www.ic.nhs.uk/services/qof. 9 Szczech R, Narkiewicz K, Bieniaszewski L, Kosmol A, Krupa-Wojciechowska B. The prevalence of home blood pressure monitoring among hypertensive females and males – polish hypertension survey. Am J Hypertens 2001; 14: 44A. 10 Krecke H-J, Lutkes P, Maiwald M. Patient assessment of self-measurement of blood pressure: results of a telephone survey in Germany. J Hypertens 1996; 14: 323–326. 11 Hahn LP, Folsom AR, Sprafka JM, Prineas RJ. Prevalence and accuracy of home sphygmomanometers in an urban population. Am J Public Health 1987; 77(11): 1459–1461. 12 Demunter C How skilled are Europeans in using computers and the Internet? – Eurostat Statistics in Focus. European Commission 2006. No. 17 [cited 24 4 2007]. Available from: http://epp.eurostat.ec.europa. eu/cache/ITY_OFFPUB/KS-NP-06-017/EN/KS-NP-06017-EN.PDF. 13 Hond ED, Celis H, Fagard R, Keary L, Leeman M, O’Brien E et al. Self-measured versus ambulatory blood pressure in the diagnosis of hypertension. J Hypertens 2003; 21: 717–722. 14 Little P, Barnett J, Barnsley L, Marjoram J, FitzgeraldBarron A, Mant D. Comparison of acceptability of and preferences for different methods of measuring blood pressure in primary care. BMJ 2002; 325: 258–259. 15 British Hypertension Society 2007 [updated 2007; cited 24 4 2007] Available from: http://www.bhsoc. org/blood_pressure_list.stm.

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