OBJECTIVES: To propose a single score for quality of life (QoL) derived from the SF-36 and the HAQ in patients with APS in a tertiary care center. METHODS: It is a cohort study. Sample was stratified in two groups according to the numbers of changes in the warfarin dosage over a period of 12 months: Group 1 (<6 changes in 12 months) and Group 2 (>6 changes in 12 months). This change was due to INR oscillation. To assess quality of life, SF-36 and HAQ instruments at baseline and after 12 months of follow-up were used. To derive the single score, a descriptive analysis evaluated the variables. Principal component analysis (PCA) was done to reveal the internal data structure that explains the data variance. APS score was calculated by the sum of the values obtained by weighting the factor scores for each component by the proportion of variability explained by the respective component. To measure APS score consistency to patient’s preference, we based on the hypothesis that Group 2 had a worse quality of life. To test it, we evaluated APS score into the two time points.. To corroborate these results, we applied repeated measures ANOVA technique. For all statistical tests, the significance level used was < 5%.  RESULTS: Group 1: 37 and Group 2: 17 individuals. The descriptive analysis indicates that Group 1 has superior QoL than Group 2. After this step, the minimum and maximum APS score was obtained: From - 2.86905 to + 2.797845. Higher score means the higher the QoL. In order to corroborate our hypothesis, repeated measures ANOVAresults verified that there are significant differences between the two groups [F (14.27) = 24.13, p=0.0004].  CONCLUSIONS: APS score is a valid instrument to measure QoL in APS patients.