A graphic nomogram for warfarin dosage adjustment

We assessed the ability of a graphic nomogram to adjust steady-state warfar in dosages and to predict international normalized :ratios (INR) after a do sage change, compared with an anticoagulation clinic pharmacist and a Bayes ian regression computer program. Study subjects were 108 men and 3 women re ceiving warfarin anticoagulation. Tn all patients the median absolute error s in predicted INR values for the nomogram, computer program, and pharmacis t were 0.33, 0.46, and 0.48, respectively. The nomogram was significantly m ore precise than both other methods (p=0.036). In a subset of 50 patients w ho required dosage reductions, the median absolute INR prediction errors fo r the nomogram, computer program, and pharmacist were 0.35, 0.54, and 0.48 respectively. The nomogram was significantly more precise than the pharmaci st (p=0.005) and computer (p=0.002). The ability to provide more precise do sage reductions of warfarin may be of clinical importance in light of curre nt recommendations for higher-intensity warfarin therapy and maintenance of higher INR values. Prospective validation of the performance of this nomog ram in a routine clinical setting is warranted.