Background: Hypertension (HTN) is one of the most important health problems in Thailand and worldwide. The accuracy of diagnosis of HTN is crucial to avoid adverse reactions from medications and reduce treatment costs. In 2011, The National
Institute for Health and Clinical Excellence (NICE) recommended a diagnostic guidelines for hypertension using ambulatory blood pressure monitoring (ABPM) aiming to exclude patients with white coat hypertension (WCH). We investigated the prevalence of HTN in suspected hypertensive patients at Rajavithi Hospital according to the NICE guidelines and factors associated with WCH.
Objective: To determine the prevalence of HTN in suspected hypertensive patients at Rajavithi Hospital according to the NICE
guidelines (using ABPM)and risk factors associated with WCH.
Material and Method: This cross-sectional study enrolled 31 subjects, age 18-80 years, with systolic blood pressure (SBP)
>140 mmHg and/or diastolic blood pressure (DBP) >90 mmHg in the Outpatient Department at Rajavithi Hospital from March 2012 to December 2012. All participants had never had a diagnosis of HTN or been treated with anti hypertensive medications in the past four weeks. 24-hour ABPM was used to confirm the diagnosis of HTN based on daytime average blood pressure >135/85 mmHg. Subjects with an average daytime blood pressure below 135/85 mmHg were defined as having WCH.
Results: Among 31 subjects, 17 (54.8%) were confirmed to have HTN and 14 (45.2%) had WCH. Subjects with true HTN had a mean clinical blood pressure of 157.88+7.68/94.24+6.56 mmHg when measured at the initial presentation using a sphygmomanometer, whereas subjects with WCH had a mean clinic blood pressure of 148.18+7.06/89.39+4.10 mmHg. Mean SBP and DBP were significantly lower among WCH subjects (p = 0.001 and p = 0.018 respectively). Age, sex, smoking, alcohol consumption, BMI, lipid profile, uric acid and hemoglobin levels were not associated with the diagnosis of WCH.
Conclusion: The prevalence of hypertension in suspected hypertensive patients using ABPM was 54.8%. WCH should be
suspected in patients with relatively lower clinic BP. We proposed that ABPM should be used to confirm the diagnosis of HTN
according to the NICE guidelines as a standard practice among ambulatory patients suspected of having HTN.

Keywords: Hypertension (HTN), White coat hypertension (WCH), Ambulatory blood pressure monitoring (ABPM), Clinical
blood pressure (BP)