Troponin T (high sensitivity)

The upper limit, 14 ng/L for the assay used in most UK hospitals, is the level below which 99 out of 100 healthy adults fall. It sits a little higher in older people and in kidney disease in the general population. Ranges differ between assays, and the change between two samples a few hours apart matters more than one figure.

Troponin T is a protein found inside heart muscle cells that leaks into the blood when those cells are injured. The high sensitivity version of the test can pick up amounts far smaller than older tests could, so tiny quantities are found in healthy people. Troponin T and troponin I are two different proteins from the same muscle machinery; hospitals use one or the other.

Doctors request it in hospital when someone has chest pain, breathlessness or collapse, to look for injury to the heart muscle. It is usually repeated a few hours later because the change between two samples is more informative than either on its own.

• A heart attack
• Other strain on the heart, such as a very fast heart rhythm, heart failure, or inflammation of the heart muscle
• Very hard exercise, such as a marathon
• Kidney disease, because small amounts are released continuously and cleared more slowly
• Serious infection, a blood clot in the lung, or a stroke
• Older age, in small amounts, in the general population

• A fall between two samples is what doctors expect as the heart recovers after an injury
• Values near zero are usual in healthy adults; there is no lower limit
• Newer, more sensitive assays report small numbers that older assays would have called undetectable

• Strenuous exercise in the day before the test
• Kidney disease raises the resting level in the general population without any new heart injury
• Some people carry antibodies that interfere with the assay and give a falsely high figure
• A haemolysed sample (red cells broken during collection) can give a falsely low figure

No preparation needed. The timing of the sample in relation to the onset of symptoms, and the change between two samples a few hours apart, are what the doctors look at. A single old result on its own tells little.

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