The fact that 5% of otherwise healthy individuals will fall outside the normal range is important when looking at laboratory results-finding a value outside of the reference range does not automatically represent an abnormality. Someone one inch taller than the 95% CI is not necessarily a giant, and someone one inch shorter does not necessarily have a growth issue. Using the measurement of height as an example, healthy individuals can be just above or just below a normal range (or 95% CI). This is one of the challenges with using statistical methods to define a normal range and must be remembered when evaluating a test result falling near either end of the reference range. It is important to note that when the definition of the normal range is set as a 95% CI, 2.5% of healthy individuals will be below the range, and 2.5% will be above, even though they were originally selected as being healthy. These results are used to determine what the normal range is using a variety of statistical approaches.Ī common statistical measurement is called a 95% confidence interval (95% CI), which is the range that includes 95% of the results from healthy tested subjects (as in a bell curve). To determine what is normal, the laboratory test is performed on a group of healthy individuals, usually adults and equally divided between males and females. Proper interpretation of any laboratory value depends on comparing the result to the appropriate established normal reference ranges, which are age-specific in some cases. In the past, genetic tests were available mainly in research settings, but now, several commercial labs offer genetic sequencing for the identification of known mutations causing various types of PI. The most common laboratory tests used to evaluate immune disorders identify:Īnother emerging laboratory test for the diagnosis of PI is genetic testing. If the clinical problems include infections, information regarding the types of microorganisms causing infection, the sites of infection, and the therapies required to treat the infections often help focus the laboratory studies. This typically begins with screening tests, followed by more sophisticated (and costly) tests chosen based on the screening test results. These tests are usually prompted by the individual experiencing clinical symptoms, particularly recurrent and/or chronic infections.Īn accurate medical history, family history, and physical examination are critical in developing the best strategy for laboratory evaluation. Laboratory tests are necessary to determine if an individual has a primary immunodeficiency (PI).

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