Advancing clinical practice in the management of Deep Vein Thrombosis: development, application and evaluation of the Autar DVT scale

Deep Vein Thrombosis (DVT) is a disease of hospitalised patients and is a precursor of Pulmonary Embolism (PE), a potentially fatal complication. DVT and PE are preventable and venous thromboprophylaxis consensus groups recommend that patients be risk assessed and accordingly receive appropriate prophylaxis. The Scope of Professional Practice (UKCC, 1992) enables nurses with appropriate knowledge and clinical competence to explore· new territories, previously the exclusive province of doctors. In the spirit of the position statement of professional practice framework, the Autar DVT scale (1994) was developed to identify patients at risk, so that appropriate venous thromboprophylaxis can be initiated. The scale is composed of seven categories of risk factors derived from Virchow's triad in the genesis of DVT. In this study, the DVT scale was re-validated on 150 patients across three distinct clinical specialities in order to allow for generalisation of the findings. DVT is a continuing problem and for this significant reason, the patients were followed up for a minimum of three months after discharge from hospital. Interestingly, 39 per cent of the patients with DVT (11/28) developed this insidious condition at home. Five reproducibility studies on the orthopaedic, medical and surgical directorates achieved kappa values ranging between 0.88 to 0.95, confirming the consistency of the instrument. A Receiver Operating Characteristic (ROC) curve was constructed to determine the optimal predictive accuracy of the DVT scale and a cutoff score of 11 yielded approximately 70 per cent sensitivity. Data from two patients, who could not be followed up, on account of discharge to no fixed abodes, were excluded for the sensitivity analysis of the DVT scale. Overall, 115 patients out of the 148 (78%) were correctly classified. However, the administration of venous thromboprophylaxis masked the predictive efficiency of the DVT scale in relation to its sensitivity and specificity. A high predictive value of 84 per cent of negative outcome was achieved at the cost of a predictive value of 37 per cent of positive outcome. The DVT scale exhibited good clinical and practical application. Data extrapolation also suggests that although the clinical areas use some venous thromboprophylaxis strategies, in practice they are not consistently applied.