What defines the laboratory normal range for clinical trials?

• A. A average value derived from only one study
• B. An expected set of values representing healthy individuals
• C. The absolute best values across all patients
• D. A range that varies completely by trial location

Answer: (B)

The laboratory normal range for clinical trials is defined as an expected set of values representing healthy individuals. This range provides a reference point against which individual patient results can be compared to determine if those results fall within typical limits indicative of health or if they may suggest a potential health issue. Establishing this normal range involves statistical analysis of data from a significant number of healthy participants to ensure that the values accurately represent the population.

This approach allows researchers to identify outliers and ensure that any deviations in test results from healthy ranges are meaningful in the context of the trial. The development of such ranges takes into account various demographic factors such as age, sex, and ethnicity, ensuring that the reference values are relevant and applicable to the trial population.

The other options either suggest too narrow a focus, like deriving values from a single study or identifying absolute 'best' values, which do not capture the variability and distribution of healthy populations, or imply that the values can vary arbitrarily by location, which would undermine consistency and comparability in the clinical trial results.