Name common sources of observer bias in BP measurement?

• A. Only random error due to cuff size.
• B. Observer bias is not a concern in clinic BP.
• C. Expectation bias, rounding readings, pressing to finish quickly, or referencing prior results without rechecking.
• D. Using the automatic device eliminates bias.

Answer: (C)

Observer bias in BP measurement happens when the clinician’s expectations or the measurement workflow influence the reading rather than the patient’s true blood pressure. The most common sources are expectation bias—wanting the patient to have high or low BP and letting that belief color the result—rounding readings to convenient or familiar numbers, feeling pressed to finish quickly which can rush technique, and referring to a prior result without rechecking the current measurement. These biases are driven by human judgment and how the measurement is carried out, not by the device itself.

Cuff size affects accuracy as a technical error, not observer bias, and using an automatic device reduces but does not completely eliminate bias because human factors can still influence how measurements are taken or interpreted.