What is the rule of CV acceptability in method validation?

• A. CV < 1%
• B. CV < 5%
• C. CV < 10%
• D. CV < 20%

Answer: (B)

Precision is measured by the coefficient of variation, and in method validation you want repeated measurements to be tightly clustered around the mean. A CV under 5% shows good repeatability and intermediate precision across runs, which is typically considered an acceptable level for validating analytical methods used in clinical chemistry. It keeps measurement noise from obscuring true differences between samples, supporting reliable results in practice. A CV of 1% is very stringent and often impractical for many assays; a CV of 10% or 20% would indicate substantial variability, undermining confidence in the method’s precision. Therefore, CV less than 5% is the best standard among these options.