If a biochemical test gives the same reading for a sample on repeated testing, it shows that the test is?

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2021

Biochemistry and Nutrition

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2021

Explanation

Precision, also known as reproducibility, refers to the ability of a test to yield consistent results when the same sample is tested multiple times.
The question describes a scenario where a test gives the 'same reading' on 'repeated testing', which is the exact definition of precision.
A high-precision test has low random error, meaning the results are tightly clustered together, regardless of whether they are close to the true value.

Option A: Accuracy refers to how close a measurement is to the true or accepted value. A test can be precise (consistent) without being accurate (correct). For example, a scale that is not calibrated correctly might consistently show your weight as 5 kg heavier than it is; it is precise but not accurate.
Option C: Sensitivity is a measure of how well a test can identify true positives. It is the ability of a test to correctly identify individuals who have a specific disease or condition.
Option D: Specificity is a measure of how well a test can identify true negatives. It is the ability of a test to correctly identify individuals who do not have a specific disease or condition.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Principles of laboratory test validity: Precision vs. Accuracy as background academic context rather than a clinical decision trigger.
Nurses must understand the difference between precision and accuracy to critically interpret lab results. A point-of-care device might be precise (giving consistent readings) but inaccurate due to poor calibration, leading to incorrect clinical decisions.
Understanding these concepts helps in quality control. If a nurse notices a patient's glucose readings are consistently high on one machine but normal on another, they can suspect an accuracy issue with the first machine and report it for calibration.
What if? A hospital's lab instrument is highly precise but not accurate for potassium levels, consistently reporting them 0.5 mEq/L lower than the true value. A patient with a true potassium of 3.3 mEq/L (mild hypokalemia) might show a result of 2.8 mEq/L (moderate-severe hypokalemia), triggering an unnecessary and potentially dangerous IV potassium infusion.

How to Approach the Question

First, break down the question's core statement: 'gives the same reading for a sample on repeated testing'.
Identify the key concepts in this statement: 'same reading' implies consistency, and 'repeated testing' implies reproducibility.
Next, review the definitions of the options. 'Accuracy' relates to correctness, 'Precision' relates to consistency, 'Sensitivity' relates to detecting true positives, and 'Specificity' relates to detecting true negatives.
Match the concept of consistency/reproducibility from the stem with the correct definition from the options.
Conclude that 'Precision' is the term that describes getting consistent results upon repetition.

Concept Tested & Keywords

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E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) p. 553-555

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart B (pp 240-463 of 478) p. 84-86