Testing for thrombophilia: clinical update

Thrombophilia describes inherited and acquired prothrombotic states which predispose to venous, but not arterial thromboembolism. The heritable states are of limited clinical significance in primary care and while they may underlie a patient’s presentation with deep venous thrombosis (DVT) or pulmonary embolism (PE) of uncertain cause, tests infrequently alter management. Testing patients is not without pitfalls: results are only informative if taken in the right patient at an appropriate time, as explained in recent guidance from the National Institute for Health and Care Excellence (NICE)1 and described below. The inherited thrombophilias are described in greater detail in Box 1 and largely fall into one of two groups: common low thrombosis-risk states, such as activated protein C resistance (due to the Factor V Leiden mutation) and rarer higher-risk states, including protein C or S deficiency. Due to their rarity, epidemiological data around some of the thrombophilias are poor: guidelines on these from NICE and the British Society for Haematology are largely expert opinion based on limited observational data.1,2 #### Box 1. Typical components of a thrombophilia blood panel ##### Inherited states