By The Pawline veterinary teamVeterinary-reviewed by Alastair Greenway, BVM&S MRCVS · 9 August 2026
Reference range · fLDogs
9.119.4
Reference
9.1–19.4
Direction
Both unusually high and low values carry meaning.
This is the conventional reference interval. Your pet’s own report may print a slightly different range, so always read the value against that. Sign in to see your pet’s value on this strip.
PDW describes how much platelet size varies within a sample. A wide spread often accompanies a marrow actively replacing platelets, but it is a supporting detail rather than a finding in its own right — it is read next to the platelet count and MPV, and in cats it is easily distorted by clumping.
PDW is one of the platelet indices a haematology analyser reports alongside the platelet count itself. Where MPV is the average platelet size, PDW describes the spread of sizes around that average — a narrow figure means the platelets are much of a muchness, a wide one means the sample holds a mixture of small and large.
PDW describes how much platelet size varies. Larger, younger platelets entering the circulation widen the spread.
What a wide result can reflect
Platelets released in a hurry tend to be larger than those produced at a steady rate, so a marrow actively replacing platelets can produce a mixed population and a wider PDW. That most often accompanies increased platelet turnover — consumption, destruction or recovery after a period of low platelets (eClinpath).
It is worth being clear about how far this can be taken. PDW is not specific: it does not say why turnover is raised, and a wide spread with a normal platelet count and no other abnormality is often of no consequence at all. It earns its place as context for the platelet count rather than as a finding to act on.
Reading a normal result
A PDW inside the interval says the platelet population is fairly uniform. It carries no reassurance about platelet number — that is the platelet count's job — and a normal PDW alongside a low count does not soften the low count.
Why the number moves for non-biological reasons
Platelet indices are more analyser-dependent than most results. They are calculated from how a machine sizes particles, so a different analyser can report a genuinely different figure on the same blood, and the reference interval belongs to the instrument rather than to the species in general. This is one reason to read the range your own report prints beside the value.
Clumping is the big one. Platelets stick together readily, and clumps are sized as though they were single large platelets — which inflates both MPV and PDW and deflates the count. Feline platelets clump notoriously easily, so feline platelet indices are frequently unreliable and a laboratory may flag or suppress them altogether (eClinpath).
Cat vs dog
The principle is the same in both, but the practical value is lower in cats for the clumping reason above. A wide feline PDW is at least as likely to reflect the sample as the animal, and a blood smear examined by eye settles it in a way no index can.
In chronic disease
PDW is not used to monitor a diagnosed condition on its own. Where platelets are being followed — during treatment that suppresses the marrow, or while a low count recovers — the count is the number that matters, with the indices read as supporting texture around it.
Reference ranges reflect conventional laboratory intervals. Always interpret against your own lab's printed range and your veterinary surgeon's judgement. A brighter optimal band is shown only where a published guideline defines one, and it is cited.
This page is educational and is not a diagnosis. Lab results are interpreted in the full clinical context by your veterinary surgeon; a single value rarely tells the whole story.
