A new glucometer gives readings that vary by less than 2 mg/dl when the same blood sample is tested repeatedly, but it reads approximately 40 mg/dl higher than the reference laboratory value every time. The instrument is best described as:

• A Both valid and reliable
• B Valid but not reliable
• C Reliable but not valid ✓
• D Neither valid nor reliable

Explanation

Reliability (reproducibility or precision) is the ability of a test to give consistent results on repeated application; validity (accuracy) is the ability to measure what it is supposed to measure, judged against a gold standard. A systematic error of 40 mg/dl destroys accuracy despite excellent repeatability, so the meter is reliable but invalid. Random variation would have harmed reliability instead.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.