daytime ambulatory systolic BP was 7 mm Hg higher than the corresponding SPRINT clinic BP in the intensive treatment group and 3 mm Hg higher than clinic BP in the standard treatment group (corresponding numbers were 6 and 5 mm Hg for diastolic BP). Observational studies have demonstrated that this type of masked effect, with higher ambulatory than clinic BPs, is associated with increased risk for CVD and all-cause mortality.17 On the other hand, white-coat hypertension (elevated clinic BP and normal ambulatory BP) is associated with lower risk for adverse outcomes. This is increasingly Table 2. Studies evaluating effect of different BP measurement protocols Author Population Protocol 1 Protocol 2 Notes Method BP Method BP A. Studies comparing specific components of BP measurement protocols Mourad et al.29 Normotensive Arm dependent 113/72 Arm horizontal 103/62 Similar results observed for ambulatory BP monitoring Hypertensive Arm dependent 163/88 Arm horizontal 145/79 Webster et al.30 Hypertensive Arm dependent 158/104 Arm horizontal 140/90 Adiyaman et al.31 Hypertensive Legs crossed 147/88 Legs uncrossed 140/86 Patients with diabetes Legs crossed 138/76 Legs uncrossed 130/74 Fonseca-Reyes et al.32 Large arm circumference Standard cuff 125/80 Large cuff 118/74 Prevalence of large arm circumference .40% in family medicine and hypertension clinics B. Studies comparing “routine” and guideline-adherent BP measurement protocols Myers et al.33 Hypertensive “Routine” office 146/87 “Research RN” 137/78 Routine office BP was average over prior 3 mo Graves et al.34 Hypertensive “Routine” office 152/84 AHA method 138/74 Routine office BP at time of referral for ABPM Brown et al.35 Hypertensive “Routine” office 161/95 Formally trained RNs 152/85 Routine office BP at time of referral for ABPM Ray et al.36 Hypertensive “Routine” office 133/78 AHA method 134/80 Random order; 93% of patients results differed by $5 mm Hg SBP or $2 mm Hg DBP C. Studies comparing manual and automated BP measurement protocols Campbell et al.37 Firefighters BpTRU 120/76 Standardized 122/78 Random order of measurement Edwards et al.38 Hypertensive BpTRU 136/74 Standardized 144/77 Retrospective; standardized BP before BpTRU in all patients Myers et al.39 Adults BpTRU 115/71 Standardized 118/74 Random order of measurement Filipovský et al.40 Hypertensive BpTRU 131/78 Physician 147/86 BpTRU first in all patients; no standard protocol for physician BPs RN, registered nurse; ABPM, ambulatory blood pressure monitor; SBP, systolic blood pressure; DBP, diastolic blood pressure. Table 3. “Clinic” versus ambulatory BP in prior clinical trials and observational studies Study Clinic SBP Daytime Ambulatory SBP Δ Systolic BP SPRINT ,140 mm Hg group 135.5614 138.8613 +3.3 SPRINT ,120 mm Hg group16 119.7613 126.5612 +6.8 AASK cohort20 133.6617 137.6617 +4.0 CRIC21 126.4620 132.3616 +5.9 HOPE10 151620 156620 +5.0 Values presented are mean 6 SD. CRIC, Chronic Renal Insufficiency Cohort; HOPE, Heart Outcomes Prevention Evaluation. J Am Soc Nephrol 29: 383–388, 2018 BP Measurement Technique 385 www.jasn.org BRIEF REVIEW important because guidelines, including from the AHA and the US Preventative Services Task Force, recommend out-ofoffice BPs in the diagnosis and management of hypertension.2,18 Despite these recommendations, the BPs used to define eligibility and BP targets in all major hypertension trials have been office based; whether targeting ambulatory versus clinic BP reduces risk for adverse outcomes is unknown, and represents an important research need in future studies. In clinical practice, daytime ambulatory BPs are often lower than clinic BPs. Interestingly, this observation is not seen in clinical trials, where daytime ambulatory BPs have been found to be higher than clinic BPs. This finding may be due, in part, to the use of protocolized clinic BP measurement in clinical trials. Examples include the Heart Outcomes Prevention Evaluation and AASK trials as well as theChronicRenal InsufficiencyCohort observational cohort study (Table 3).19–21 Additional factors that may have contributed to lower daytime ambulatory relative to clinic BP in SPRINT include: (1) participants had attended at least 13 prior SPRINT visits which may reduce any potentialwhite-coat effect and (2) the potential, albeit unknown, effect of the unobserved automated measurement technique. Although direct comparisons to BPs in routine clinical practice aren’t available in SPRINT, it is likely that the protocolized research clinic BPs were lower. This leads to an inevitable question: what systolic BP shall one target if one wants to use the evidence from SPRINT in clinical practice? The SPRINT results have at least two important implications for clinical practice. First and foremost, providers caring for patients at high risk for CVD should consider targeting a more intensive systolic BP goal, with a target of ,120 mm Hg. Second, targeting a lower clinic BP necessitates adherence to clinic BP measurement techniques used in trials for measuring BP. At lower BPs, the importance of accurate measurement may be particularly important. For example, patients with a systolic BP just above 120 mm Hg using routine clinic BPs may have a systolic BP ,110 mm Hg when measured appropriately. Such a