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Gas transfer per litre (KCO)

Breathing tests · also printed as KCO, DLCO/VA, TLCO/VA, Transfer coefficient, Kco

Typical UK adult rangeNo single typical range

No fixed range; compare with the printed predicted value.

What this test measures

KCO is the gas transfer divided by the lung volume in which it was measured. It shows how efficient each litre of lung is, separating small lungs from damaged ones.

Why doctors request it

Read alongside TLCO to work out why gas transfer is low, since a small lung and a damaged lung give different patterns.

What commonly pushes it up

Small but healthy lungs, for example after lung surgery or with a weak chest wall
Bleeding into the lungs

What commonly pushes it down

Emphysema
Lung fibrosis
Circulation problems in the lung

Everyday reasons for a value outside the range

Predicted values depend on age and sex

About the sample

Same test session as TLCO.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.

Got a report with Gas transfer per litre (KCO) on it?

Upload a photo or PDF and see every line against the range your lab printed, explained in plain English. First report free.

Read my report free

This is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.