Vibrant reports antibodies expressed as arbitrary units (AU).
In laboratory medicine, AUs are relative, non-standardized measurements used when an absolute unit (like mg/dL) isn't practical or defined, often representing intensity or binding based on a specific lab's reference sample and procedure.
AUs are set by the specific testing method (e.g., how brightly antibodies glow in a fluorescent tag) or a reference sample used by a particular lab.
Key Characteristics
- Procedure-Defined: AUs are set by the specific testing method (e.g., how brightly antibodies glow in a fluorescent tag) or a reference sample used by a particular lab.
- Relative, Not Absolute: They show relative levels (e.g., one sample has twice the AU of another) rather than a fixed quantity in system international (SI) units (e.g., grams or liters).
- Not Always Comparable: "1 AU" from Lab A might not equal "1 AU" from Lab B, requiring knowledge of the underlying method and reference.
- Qualitative/Semi-Quantitative: They provide a sense of magnitude or trend but are less precise than standardized units.
Other Examples in Medicine
- Antibody Testing: Used in tests for antibodies (like for COVID-19 or autoimmune diseases), where a positive control serum is assigned a value (e.g., 100 AU/mL) and other samples are compared to it.