Interchangeability of ambulatory and office blood pressure: limitations of reproducibility and agreement.
A possible equivalence of office (Off) patient-recorded blood pressure (BP) and ambulatory (Amb) BP was evaluated. The criteria were the between-visits reproducibility (R) of oscillometrically measured supine office (Off), seated Off, and 24-h Amb BP and the agreement between Off and Amb data. Randomly ordered sessions were completed within 4 months in 59 untreated patients with Amb 24-h BP 136/87 (SD 14/10) mmHg and HR 72 (SD 9). R improves as SD of differences between sessions decreases with the number (n) of values included in the average so that SDD = a n(-b), where a and b are constants for each method, data sampling strategy, and group. R of a few steady Off data is better than R of a few Amb data. As n of the averaged values increases, R of Off and Amb methods converges and with n approximately 24 becomes identical. Only further increase in n of Amb data makes R of the Amb method superior than the Off method. The variably elevated initial Off BP distorts R and agreement. After approximately 6 readings, Off BP stabilizes at a lower "steady" level. "Steady" data averaged over visits are close to the Amb 24-h average from two sessions. Supine Off "steady" level is close to supine levels before sleep. The Off versus Amb method agreement improves by averaging "steady" BP from one up to four Off sessions, up to 7 "steady" Off readings over a session, and BP in both arms. At best the SBP agreement is within +/- 7.6 mmHg in 90% of cases with 24-h Amb S/D BP ranging 115-155/75-105 mmHg. The casually elevated BP can be evaluated only by the demonstrated between-visits reproducible 24-h Amb average or by the nearly equivalent average of multiple "steady" data from two to four Off visits.
Pavek
K
K
Department of Information Science, University of Uppsala, Sweden. Karel.Pavek@telia.com
Taube
A
A
D000328:Adult; D000368:Aged; D001794:Blood Pressure; D001795:Blood Pressure Determination; D018660:Blood Pressure Monitoring, Ambulatory; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results