**Question:** Using a new technique, Hemoglobin was estimated in a blood sample. The test was repeated for 10 times. The repos were 9.5, 9.2, 9.4, 9.6, 9.7, 9.9, 10.5, 12.1. Accurate value of Hb was estimated by standard test to be 10.2. The new technique has:

A. high variability (as indicated by a range from 9.2 to 12.1)
B. consistently low results (with a mean of 9.8)
C. consistently high results (with a mean of 10.3)
D. a coefficient of variation (CV) greater than 10%

**Correct Answer:** D. a coefficient of variation (CV) greater than 10%

**Core Concept:** Hemoglobin (Hb) is a protein found in red blood cells (RBCs) that carries oxygen from the lungs to the body's tissues and returns carbon dioxide back to the lungs. Hb estimation is a crucial test in clinical practice for detecting anemia, polycythemia, or assessing the severity of these conditions.

**Why the Correct Answer is Right:** The coefficient of variation (CV) measures the dispersion or spread of the data around the mean, indicating the precision of the test. A CV greater than 10% suggests poor precision or accuracy of the test.

**Why Each Wrong Option is Incorrect:**

A. High variability does not necessarily mean poor precision or accuracy. Variability is simply the range of values obtained from repeated measurements.
B. Consistently low results indicate that the new technique overestimates Hb levels, but precision (CV) is the key concern here, not the mean value.
C. Consistently high results indicate that the new technique underestimates Hb levels, but precision (CV) is the key concern here, not the mean value.
D. A CV greater than 10% demonstrates poor precision or accuracy of the test, as explained above.

**Clinical Pearl:** A CV of 10% or less indicates a reliable Hb test result, while a CV greater than 10% highlights a need for further investigation, such as using a different technique or confirming the result with a more reliable test.