Table 3.
Sources of inaccuracy in the measurement of blood pressure in the clinic setting.
| Effect on SBP, mm Hg | Effect on DBP, mm Hg | |
|---|---|---|
| Before measurement | ||
| Acute meal ingestion | − 6 | −5 to −1.9 |
| Acute alcohol consumption | −23.6 to +24 | −14 to +16 |
| Acute caffeine consumption | +3 to +14 | +2.1 to +13 |
| Acute nicotine use or exposure | +2.8 to +25 | +2 to +18 |
| Bladder distension | +4.2 to +33 | +2.8 to +18.5 |
| Cold exposure | +5 to +32 | +4 to +23 |
| Insufficient rest period | +4.2 to +11.6 | +1.8 to +4.3 |
| Device | ||
| Use of a non-validated device | 0% to 70% with ≥ ±3† | 0% to 70% with ≥ ±3† |
| Device not calibrated | 0% to 70%† | 0% to 70%† |
| Patient positioning | ||
| Standing versus sitting | −2.9 to +5.0 | +7 |
| Supine versus sitting | −10.7 to +9.5 | −13.4 to +6.4 |
| Legs crossed at the knee | +2.5 to +14.9 | +1.4 to +10.8 |
| Unsupported back | Not significant effects | +6.5 |
| Unsupported arm | +4.9 | +2.7 to +4.8 |
| Arm lower than heart level | +3.7 to +23 | +2.8 to +12 |
| Attaching the device to the person | ||
| Paretic arm | +2 | +5 |
| Too small cuff size | +2.1 to +11.2 | +1.6 to +6.6 |
| Too large cuff size | −3.7 to −1.5 | −4.7 to −1.0 |
| Cuff placed over clothing | Not significant effects | Not significant effects |
| Stethoscope placed under cuff | +1.0 to +3.1 | −10.6 to −3.5 |
| Taking the measurement | ||
| White coat effect | −12.7 to +26.7 | −8.2 to +21 |
| Talking during the measurement | +4 to +19 | +5 to +14.3 |
| Use of stethoscope bell vs. diaphragm | −3.8 to −1.5 | −1.6 |
| Excessive pressure on stethoscope head | Not significant effects | −15 to −9 |
| Fast cuff deflation | −9 to −2.6 | +2.1 to +6.3 |
| Observer hearing deficit | −1.6 to −0.1 | +1.1 to +4.3 |
| Recording Korotkoff phase IV versus V for DBP | Not applicable | +12.5 |
| Short interval between measurements | Not significant effects | Not significant effects |
| Interpreting the measurement | ||
| Reliance on a single measurement | +3.3 to +10.4 | −2.4 to +0.6 |
| Inter-arm differences | 3.3 to 6.3†† | 2.7 to 5.1†† |
| Terminal digit preference | 1% to 79% over-representation of terminal of 0 | 3% to 79% over-representation of terminal of 0 |
DBP – diastolic blood pressure; SBP – systolic blood pressure
†
Depending on type of device used (mercury, aneroid or automated)
††
Values could be too low or too high depending on the arm used.
Adapted from N Kallioinen, A Hill, M Horswill et al. J Hypertens. 2017 Mar; 35 (3):421-441.