Comment: accuracy of store-based blood pressure monitors TO THE EDITOR: We read with interest the report by Rotch et al., 1 which compared home blood pressure (BP) monitors with a standard mercury sphygmomanometer. A computerized upper arm device was more accu- rate than wrist and finger monitors compared with an office-based mer- cury sphygmomanometer. Although patients are frequently asked to ob- tain a BP monitor and use it at home, many cannot afford such devices. These patients are often instructed to check their BP at pharmacies or other stores between clinic visits. These data are commonly used when titrating the doses of antihypertensive medications. We recently compared the BP readings of store-based BP machines with a handheld aneroid sphygmomanometer (Tycos, Welch Allyn, Ar- den, NC) commonly used in clinics. The handheld monitor was calibrat- ed to a mercury sphygmomanometer (Baumanometer, WA Baum, Copi- ague, NY). Ten passersby were checked at a local Wal-Mart with a Vita- Stat Health Station (SpaceLabs Medical, Redmond, WA), 10 were checked at Rite Aid with a CardioTech 2200 (CardioTech International, Winchester, TN), and 12 were checked at SuperSave, a local community pharmacy, with an Omron HEM 712-C (Omron, Vernon Hills, IL). The CardioTech machine measures standing BP in the forearm. The Vita- Stat and Omron readings are obtained in the upper arm while the patient is seated. Readings were obtained simultaneously in duplicate with the store machine on one arm and the handheld sphygmomanometer on the other. The cuff size of the handheld device was appropriate for all partic- ipants, and a single investigator (GH) did all measurements. The mean age of subjects (n = 32) in our study was 36.5 ± 19.6 (mean ± SD) years; 68% were women. The results are presented in Figure 1. Our results, and the results of others, 2,3 indicate that community-based BP measurements may be variable and inaccurate. Much of the variabili- ty in our investigation was attributable to the Vita-Stat machine. Others have found the Vita-Stat to be inaccurate. 3 Variability in BP monitors may not be the only problem that clinicians encounter. Johnson et al. 4 found that patients might not accurately report values obtained outside of the clinic, particularly if their BP is high. The best advice for patients appears to be to purchase a quality moni- tor that measures BP in the upper arm such as the Omron HEM-711AC reported by Rotch et al. It should be noted that the Omron HEM 712-C in our investigation was consistently high for diastolic BP; the systolic readings were also high, although these only approached statistical sig- nificance (p = 0.16). Recommended monitors should have a memory re- call feature so that clinicians may verify the readings. Finally, 24-hour ambulatory BP monitoring is an alternative tool for clinicians to compre- hensively measure BP control. 5 Gregory Hoffman MD At time of writing, Resident in Family Practice Department of Family Medicine Idaho State University Pocatello, Idaho; now in private practice Grants Pass, Oregon Rex W Force PharmD FCCP BCPS Director Family Medicine Clinical Research Center Associate Professor of Pharmacy Practice and Family Medicine Department of Family Medicine Idaho State University Campus Box 8357 Pocatello, Idaho 83209-8357 FAX 208/282-4818 E-mail force@otc.isu.edu REFERENCES 1. Rotch AL, Dean JO, Kendrach MG, Wright SG, Woolley TW. Blood pressure monitoring with home monitors versus mercury sphygmo- manometer. Ann Pharmacother 2001;35:817-22. 2. Van Durme DJ, Goldstein M, Pal N, Roetzheim RG, Gonzalez EC. The accuracy of community-based automated blood pressure machines. J Fam Pract 2000;49:449-52. 3. Whitcomb BL, Prochazka A, LoVerde M, Byyny RL. Failure of the community-based Vita-Stat automated blood pressure device to accu- rately measure blood pressure. Arch Fam Med 1995;4:419-24. 4. Johnson KA, Partsch DJ, Rippole LL, McVey DM. Reliability of self-re- ported blood pressure measurements. Arch Intern Med 1999;159:2689- 93. 5. Pickering TG. Which measures of blood pressure give the best prediction of target organ damage and prognosis? In: Pickering TG. Ambulatory monitoring and blood pressure variability. London: Science Press Ltd., 1991:13.1-13.15. 1676 ■ The Annals of Pharmacotherapy ■ 2001 December, Volume 35 www.theannals.com Figure 1. Mean blood pressure comparisons under various study conditions. at UCSF LIBRARY & CKM on April 8, 2015 aop.sagepub.com Downloaded from