A biological reference interval (BRI) is a range of values for a particular measurement that is considered to be normal for a healthy population. BRIs are used by doctors to interpret test results and to identify potential health problems.

BRIs are typically established by collecting data from a large group of healthy people. The data is then analyzed to determine the 2.5th and 97.5th percentiles, which represent the lowest and highest values that are seen in 95% of the population. The interval between these two values is the BRI.

It is important to note that BRIs are not absolute. There will always be some variation in the values seen in a healthy population. Additionally, BRIs can vary depending on factors such as age, sex, ethnicity, and health status.

If a patient’s test results fall outside of the BRI, it does not necessarily mean that they have a health problem. However, it is important to have the test results evaluated by a doctor to rule out any potential problems.

Here are some examples of BRIs for common laboratory tests:

* Blood glucose: 70-100 mg/dL

* Blood pressure: 120/80 mmHg

* Cholesterol: <200 mg/dL

* Triglycerides: <150 mg/dL

* Hemoglobin: 13-18 g/dL

* Hematocrit: 40-45%

* White blood cell count: 4,000-11,000 cells/µL

BRIs are an important tool for doctors to use in the diagnosis and management of disease. By understanding BRIs, doctors can better assess a patient’s health and make informed decisions about treatment.