Does a 24-hour ambulatory blood pressure monitor (ABPM) with less than 70% accurate readings suggest the patient removed the unit for periods of time?

Understanding Less Than 70% Accurate Readings on ABPM

Less than 70% accurate readings on ABPM does not necessarily mean the patient removed the unit, but rather indicates that insufficient valid measurements were obtained to meet quality standards for reliable interpretation. 1

Why the 70% Threshold Matters

At least 70% of blood pressure readings during both daytime and nighttime periods must be satisfactory for the monitoring to be considered interpretable, or else the study should be repeated. 1 The most recent 2024 ESC guidelines specify this requires typically ≥27 measurements over 24 hours, with preferably seven nocturnal readings obtained. 1

Common Causes of Failed Readings (Beyond Device Removal)

The 67% success rate in your patient's study could result from multiple technical factors:

• Movement artifact - The most common cause of failed readings, particularly during arm movement or physical activity 1, 2
• Improper cuff positioning - Cuff slippage or kinks in the tubing during normal activities 1
• Patient cancellation of readings - Using the cancellation button when the cuff inflates at inconvenient times 1
• Excessive physical activity - Readings during vigorous exercise or contact sports often fail 1
• Irregular cardiac rhythm - Readings may not be accurate when cardiac rhythm is markedly irregular 1
• Technical device issues - Dead batteries, device malfunction, or the patient turning the monitor off 1

Interpreting Your Patient's Results Despite Limited Data

Your patient's study shows:

• 24-hour average: 125/75 mmHg
• Daytime average: 128/73 mmHg
• Nocturnal average: 118/64 mmHg

These values fall below the 2024 ESC hypertension thresholds (24-hour ≥130/80 mmHg, daytime ≥135/85 mmHg, nighttime ≥120/70 mmHg), suggesting normal blood pressure. 1 However, because only 67% of readings were valid, this study should be repeated to ensure reliable interpretation. 1, 3

Practical Next Steps

Review the patient diary (if completed) to identify specific times when readings failed - this will clarify whether the issue was device removal versus technical failures during specific activities. 1, 3

Before repeating the study, provide enhanced patient education focusing on:

• Keeping the arm still and at heart level during cuff inflation 1
• Avoiding strenuous exercise or contact sports during monitoring 1
• Not using the cancellation button unless absolutely necessary 1
• Ensuring the device remains properly positioned throughout the 24-hour period 1
• Verifying the cuff is not kinked or twisted 1

Schedule a repeat ABPM with more frequent measurement intervals (every 20 minutes throughout both day and night) to increase the likelihood of obtaining ≥70% valid readings. 1

Critical Caveat

If the patient has atrial fibrillation or other markedly irregular cardiac rhythms, oscillometric ABPM may inherently produce unreliable readings regardless of proper technique. 1 In such cases, alternative blood pressure assessment methods should be considered.