Reference range
Key concepts ·Also called: reference interval, normal range, normal values, lab range
What it is
A laboratory establishes its reference interval by testing a group of healthy animals and taking the central 95 per cent of the results. By definition, one healthy animal in twenty falls outside it for any given test — and a panel of thirty tests almost guarantees a stray flag or two.
Why it matters
This is the single most common source of unnecessary worry when an owner reads a lab report. A value a fraction outside the range is usually noise. A value inside the range that has doubled since the last test can be far more significant. Trend beats threshold almost every time.
What it can point to
- Ranges are laboratory-specific — the same sample run on two analysers can be flagged by one and not the other, so numbers should not be compared across labs
- Age matters: growing puppies and kittens normally exceed adult ranges for alkaline phosphatase, phosphorus and several other values
- Breed matters: Greyhounds run high red cell counts and creatinine, Akitas and Shiba Inus have small red cells, Cavalier King Charles Spaniels have low platelet counts
- Being frightened at the clinic changes real numbers — glucose and white cells in cats especially
- A single flagged value in an otherwise normal panel, in an animal that seems well, is usually watched rather than chased
Questions worth asking your vet
- How does this compare with my pet's own previous results?
- Is this flag clinically significant, or just outside the statistical range?
- Would rechecking in a few weeks tell us more than investigating now?
Related terms
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