168
Letters to the Editor
Letters to the Editor Blood Pressure Monitoring 2015, 20:168–169
Blood pressure measurement reliability among different racial-ethnic groups in a stroke prevention study: methodological issues to avoid misinterpretation
applied. Otherwise, misdiagnosis and mismanagement of the patients cannot be avoided [2,3,5].
Acknowledgements Conflicts of interest
Siamak Sabour, Department of Clinical Epidemiology, School of Health, Safety Promotion and Injury Prevention Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Islamic Republic of Iran Correspondence to Siamak Sabour, MD, MSc, DSc, PhD, Department of Clinical Epidemiology, School of Health, Safety Promotion and Injury Prevention Research Center, Shahid Beheshti University of Medical Sciences, 1983535511, Tehran, Islamic Republic of Iran Tel: + 98 21 22421814; fax: + 98 21 22432036; e-mail: [email protected]
There are no conflicts of interest.
References 1
2 Received 27 September 2014 Accepted 19 November 2014 3
I read with interest the paper by Estol and colleagues published in the October 2014 issue of Blood Pressure Monitoring. The authors aimed to identify blood pressure (BP) measurement differences between clinical trial and patient determinations and among different racial-ethnic groups [1]. A total of 20 332 patients with ischemic stroke were randomized to receive antiplatelet treatment and 80 mg of telmisartan versus placebo. BP measurements were obtained at the first clinic visit and then 1 and 3 months later and every 6 months thereafter [1]. They reported BP at visits clinic 1, nonclinic 1A, and clinic 2 were, respectively, 144/84, 137/80, and 139/81 mmHg, with the difference between visits 1–2 and visit 1A being significant [1]. Considering the large sample size (N = 20 332), it is obvious that any differences that are not important clinically will be statistically significant. Therefore, clinical decision making should not be based on statistically significant findings [2,3]. On the basis of their conclusion, BP values showed differences between clinic and patient measurements, questioning the reliability of self-reported BP [1]. This conclusion may lead to a misleading message because of the inappropriate use of statistical tests to assess reliability. The reason for this is assessment of reliability; an individual-based approach instead of a group-based one should be considered [2,4]. For reliability (precision), for quantitative variables, the intraclass correlation coefficient and for qualitative variables, weighted κ should be used with caution because simple κ also has its own limitation [2,3,5]. As a take-home message, for reliability analysis, appropriate tests as well as correct interpretation should be
4 5
Estol CJ, Bath PM, Gorelick PB, Cotton D, Martin RH, Weber MA, Dahlof B. PRoFESS Publications Committee; PRoFESS Investigators. Blood pressure measurement reliability among different racial-ethnic groups in a stroke prevention study. Blood Press Monit 2014; 19:256–262. Rothman KJ, Greenland S, Lash TL. Modern epidemiology. 4th ed. Baltimore, USA: Lippincott Williams & Wilkins; 2010. Szklo M, Nieto. FJ. Epidemiology beyond the basics. 2nd ed. Manhattan, NY: Jones and Bartlett Publishers; 2007. Lin LI. A concordance correlation coefficient to evaluate reproducibility. Biometrics 1989; 45:255–268. Sabour S. Methodologic concerns in reliability of noncalcified coronary artery plaque burden quantification. Am J Roentgenol 2014; 203:W343. DOI: 10.1097/MBP.0000000000000098
Response: Blood pressure measurement reliability among different racial-ethnic groups in a stroke prevention study: methodological issues that strengthen our results Conrado J. Estola, Daniel Cottonb and Philip B. Gorelickc, aNeurological & Vascular Prevention Unit, Buenos Aires, Argentina, bBoehringer-Ingelheim Pharmaceuticals, Ridgefield, Connecticut and cSt Mary’s Health Care (Neuroscience), Grand Rapids, Michigan, USA Correspondence to Conrado J. Estol, MD, PhD, Neurology and Vascular Prevention Unit, Av. Callao 875, 3F. C1023, Buenos Aires, Argentina Tel: + 5411 4816 6733; fax: + 5411 4816 6668; e-mail: [email protected] Received 14 November 2014 Accepted 19 November 2014
We appreciate and agree with Dr Sabour’s comment. Dr Sabour reminds us that when the ‘n’ is large enough, all differences may become statistically significant and the key question, as he points out, is whether those differences are clinically relevant. We agree with the suggestion that reliability is a valid option to statistically examine the relationship between visit 1A and the other visits. We analyzed the intraclass correlation (ICC) on each pair of visits, comparing each of visits 1–5 with visit 1A on both systolic and diastolic blood pressures. The results were as follows: Systolic blood pressure ICC results compared with visit 1A: visit 1: 0.4667; visit 2: 0.4533; visit 3: 0.3710; visit 4: 0.3353; visit 5: 0.3181.
1359-5237 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Letters to the Editor
Letters to the Editor Blood Pressure Monitoring 2015, 20:168–169
Blood pressure measurement reliability among different racial-ethnic groups in a stroke prevention study: methodological issues to avoid misinterpretation
applied. Otherwise, misdiagnosis and mismanagement of the patients cannot be avoided [2,3,5].
Acknowledgements Conflicts of interest
Siamak Sabour, Department of Clinical Epidemiology, School of Health, Safety Promotion and Injury Prevention Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Islamic Republic of Iran Correspondence to Siamak Sabour, MD, MSc, DSc, PhD, Department of Clinical Epidemiology, School of Health, Safety Promotion and Injury Prevention Research Center, Shahid Beheshti University of Medical Sciences, 1983535511, Tehran, Islamic Republic of Iran Tel: + 98 21 22421814; fax: + 98 21 22432036; e-mail: [email protected]
There are no conflicts of interest.
References 1
2 Received 27 September 2014 Accepted 19 November 2014 3
I read with interest the paper by Estol and colleagues published in the October 2014 issue of Blood Pressure Monitoring. The authors aimed to identify blood pressure (BP) measurement differences between clinical trial and patient determinations and among different racial-ethnic groups [1]. A total of 20 332 patients with ischemic stroke were randomized to receive antiplatelet treatment and 80 mg of telmisartan versus placebo. BP measurements were obtained at the first clinic visit and then 1 and 3 months later and every 6 months thereafter [1]. They reported BP at visits clinic 1, nonclinic 1A, and clinic 2 were, respectively, 144/84, 137/80, and 139/81 mmHg, with the difference between visits 1–2 and visit 1A being significant [1]. Considering the large sample size (N = 20 332), it is obvious that any differences that are not important clinically will be statistically significant. Therefore, clinical decision making should not be based on statistically significant findings [2,3]. On the basis of their conclusion, BP values showed differences between clinic and patient measurements, questioning the reliability of self-reported BP [1]. This conclusion may lead to a misleading message because of the inappropriate use of statistical tests to assess reliability. The reason for this is assessment of reliability; an individual-based approach instead of a group-based one should be considered [2,4]. For reliability (precision), for quantitative variables, the intraclass correlation coefficient and for qualitative variables, weighted κ should be used with caution because simple κ also has its own limitation [2,3,5]. As a take-home message, for reliability analysis, appropriate tests as well as correct interpretation should be
4 5
Estol CJ, Bath PM, Gorelick PB, Cotton D, Martin RH, Weber MA, Dahlof B. PRoFESS Publications Committee; PRoFESS Investigators. Blood pressure measurement reliability among different racial-ethnic groups in a stroke prevention study. Blood Press Monit 2014; 19:256–262. Rothman KJ, Greenland S, Lash TL. Modern epidemiology. 4th ed. Baltimore, USA: Lippincott Williams & Wilkins; 2010. Szklo M, Nieto. FJ. Epidemiology beyond the basics. 2nd ed. Manhattan, NY: Jones and Bartlett Publishers; 2007. Lin LI. A concordance correlation coefficient to evaluate reproducibility. Biometrics 1989; 45:255–268. Sabour S. Methodologic concerns in reliability of noncalcified coronary artery plaque burden quantification. Am J Roentgenol 2014; 203:W343. DOI: 10.1097/MBP.0000000000000098
Response: Blood pressure measurement reliability among different racial-ethnic groups in a stroke prevention study: methodological issues that strengthen our results Conrado J. Estola, Daniel Cottonb and Philip B. Gorelickc, aNeurological & Vascular Prevention Unit, Buenos Aires, Argentina, bBoehringer-Ingelheim Pharmaceuticals, Ridgefield, Connecticut and cSt Mary’s Health Care (Neuroscience), Grand Rapids, Michigan, USA Correspondence to Conrado J. Estol, MD, PhD, Neurology and Vascular Prevention Unit, Av. Callao 875, 3F. C1023, Buenos Aires, Argentina Tel: + 5411 4816 6733; fax: + 5411 4816 6668; e-mail: [email protected] Received 14 November 2014 Accepted 19 November 2014
We appreciate and agree with Dr Sabour’s comment. Dr Sabour reminds us that when the ‘n’ is large enough, all differences may become statistically significant and the key question, as he points out, is whether those differences are clinically relevant. We agree with the suggestion that reliability is a valid option to statistically examine the relationship between visit 1A and the other visits. We analyzed the intraclass correlation (ICC) on each pair of visits, comparing each of visits 1–5 with visit 1A on both systolic and diastolic blood pressures. The results were as follows: Systolic blood pressure ICC results compared with visit 1A: visit 1: 0.4667; visit 2: 0.4533; visit 3: 0.3710; visit 4: 0.3353; visit 5: 0.3181.
1359-5237 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
