Clinical limitations of risk assessment models

Appropriate thromboprophylaxis in hospital patients is effective in prevent ing clinically important venous thromboembolic events, including deep vein thrombosis (DVT) and fatal pulmonary embolism. Due to the risk of bleeding associated with pharmacological prophylaxis and the cost of administering p rophylactic drugs, the clinical benefit and cost-effectiveness of thrombopr ophylaxis may be optimized by providing prophylaxis only to patients at ris k of thrombosis, and tailoring the intensity of prophylaxis to the level of risk. Accurate assessment of patients' thromboembolic risk is therefore hi ghly necessary. Thromboembolic risk is influenced by numerous factors. Seve ral risk factor indices based on clinical risk factors and laboratory varia bles have been proposed since the 1970s, but these have not been widely ado pted due to their complexity and lack of prospective validation, The method of deriving risk data on which these indices are based is questioned, and older prognostic indices excluded recently identified risk factors, particu larly molecular factors such as the clotting factor V Leiden mutation, furt her undermining their clinical value. A number of much simpler risk assessm ent models (RAMs) have now been developed which stratify patients into low- , moderate- and high-risk categories. However, no RAM currently available p rovides comprehensive guidance for all patient groups, Use of poorly design ed RAMs may fail to identify some patients at risk, leading to omission of prophylaxis and preventable thrombotic events. Certain patient groups devel op DVT despite prophylaxis. Current RAMs are not validated to identify thes e patients. Well-designed and well-validated RAMs, incorporated into standa rd practice guidelines in hospitals, should contribute to improved clinical outcomes and economic benefits of prophylaxis. (C) Lippincott Williams & W ilkins.