A multicenter evaluation of the A&D TM-2420 ambulatory blood pressure recorder.

The A&D TM-2420 (A&D Engineering, Milpitas, CA) is an automatic, portable, noninvasive blood pressure (BP) recorder which uses a dual microphone system for the detection of Korotkoff sounds. Its accuracy and clinical performance were assessed in a multicenter study that also addressed issues such as observer agreement and the effects of age, arm circumference, heart rate, posture, and blood pressure level on the observer-device differences. We compared 906 simultaneous, same-arm BP measurements in 151 subjects using the TM-2420 versus two skilled clinicians per site using a teaching stethoscope. The agreement between the TM-2420 and mercury column determinations were within 10 mm Hg for 86 to 91% of systolic readings and 91 to 94% of diastolic readings, depending on the posture; a level of agreement which would receive a 'B+' grade from the recent British Hypertension Society guidelines. The limits of agreement (2 standard deviations about the mean difference) for systolic BP between observers and the TM-2420 tended to be greater for the standing position (-20 to 15 mm Hg) compared to supine (-14 to 12 mm Hg) and seated (-13 to 8 mm Hg) positions. Limits of agreement between the observers and device were not dependent upon age, heart rate, arm size, or blood pressure level. Twenty-four-hour blood pressure monitoring in two of the four centers demonstrated an error code rate of 3.4%, excluding 'retries' that are one of the device's features. These data demonstrate an acceptable level of accuracy and performance of the sixth generation of the TM-2420 for use in clinical practice and research.(ABSTRACT TRUNCATED AT 250 WORDS)