What is the correct calibration process for a sphygmomanometer?

• A. Calibration is done by the patient once a year.
• B. Calibration not required for any sphygmomanometer.
• C. Calibration against a standard reference but no documented dates; accuracy within ±5 mmHg.
• D. Regular calibration against a standard reference; verify accuracy within ±2 mmHg; performed by qualified service personnel and record dates.

Answer: (D)

Calibration keeps readings accurate by aligning the device to a known pressure standard, preventing drift in components like the cuff, valve, or gauge over time. The best process is regular calibration against a standard reference, with an accuracy check within a tight tolerance (±2 mmHg) and performed by qualified service personnel, with the calibration dates and results documented.

This approach ensures traceability to a recognized standard, maintains clinically reliable accuracy, and provides a maintenance log for accountability. Calibrating by the patient is inappropriate, and claiming no calibration is required ignores drift over time. Using a standard without keeping documented dates and accepting a looser tolerance (±5 mmHg) reduces reliability and traceability.