Determining Reference Ranges
Laboratories establish reference ranges for tests through various methods: conducting their own studies, adopting ranges from manufacturers or other labs, or deriving ranges from existing patient data.
Defining the Reference Population
The crucial step is defining the reference population, the group of individuals represented by the reference range. Age, sex, race, health status, and medical history are factors that may influence reference populations.
Data Analysis
A significant sample (minimum 120) of individuals meeting the reference population criteria undergoes testing under standardized conditions. The results are analyzed to determine the reference range.
Statistical Analysis
For many tests, reference ranges encompass the values falling within the middle 95% of the distribution in the reference population.
Units of Measurement for Reference Ranges
Different units of measurement are used for reference ranges:
* Deciliters (dL): Commonly used in the United States
* Litres (L): Utilized in countries like Sweden
* International Units (IU): Based on biological activity or mass equivalence
* Molar Concentration (mol/L): Predominantly used in the United Kingdom, Europe, Australia, and New Zealand
* Mass Concentration (g/dL or g/L): Customarily employed in the United States
Clinical Context
Reference ranges for blood tests aid healthcare professionals in interpreting the results of medical tests obtained from blood samples. They are determined within the field of clinical chemistry, a subspecialty of pathology focused on analyzing bodily fluids.
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