- Platelet aggregation inhibitors, also known as antiplatelet therapy (APT), are prescribed for the prevention of secondary cardiovascular events (CVE) after endovascular revascularization procedures.- Platelet aggregation inhibitors are not equally effective in all patients. The phenomenon of high residual platelet reactivity despite APT is called 'high on-treatment platelet reactivity' (HTPR); it bears an increased risk of secondary CVE.- Platelet function tests (PFT) can be used to diagnose HTPR. There are various tests available; of those, light transmission aggregometry (LTA) is considered the gold standard. Some tests are only suitable for determining the effect of a certain category of APT.- Research into the usefulness of PFTs to optimise treatment with APT has not yet produced an unambiguous conclusion.- Currently there is not yet an indication for routine use of PFT in clinical practice. However, for the treatment of certain categories of patients with thromboembolic disease - such as those with renal failure or a history of kidney transplant - PFT can be considered.