Factors predicting of warfarin dosage and Factors Related to International Normalized Ratio (INR) of the patients , Nong Phok hospital, Roi Et Province.

Abstract

Purposes : Factors related to prediction of warfarin dosage and International Normalized Ratio (INR) of the patients , Nong Phok hospital, Roi Et Province.

Research design : Cross - sectional analytical research

Materials and methods : All of 58 subjects registered at warfarin clinic between July 1,2017 and July 1,2018 as an inclusion criteria with at least 3 months of treatment and 1 INR follow up. The tools and instruments consisted of 3 parts :  1) a questionnaire involved in general data such as age, gender, marital status, educational level, weight, height, indication for drug use and co–Mmorbidities;  2) a questionnaire involved health and social behavior, drinking, smoking, using herb dietary supplements interaction with warfarin and medication adherence; 3) an assessment form for collected data on INR and warfarin dosage from the Hos–xP computer program and manual patient’s records. The statistics of this research were descriptive, analytical statistics, multiple linear regression, and Chi – square test.

Main findings : All of both genders participants were equal proportions, mean of age 59 years, couple of marital status were 91.4%, primary education level 67.2%, need for warfarin to treat valvular heart disease 36.2%, atrial fibrillation 29.3%, artificial rheumatic heart valve 17.2%, patients with thromboembolic events 12.1% and other co - morbidities 51.7%.  All of fifty subjects divided into 2 groups according to the INR level: group 1 (INR 2.0 – 3.0) and group 2 (INR 2.5-3.5) and followed up 328 visits. The result of warfarin optimal dose in group 1 was 2.99 ± 1.21 mg/day based on followed  up 145 visits, and 3.86 ± 1.51 mg/day as followed up 39 visits in group 2. Factors related to prediction of warfarin dosage were age, height and body weight in group 1, and age and medication compliance in group 2 were statistically significant (252 and 76 followed up visits group1,2 respectively). Factors related to appropriate INR levels were medication compliance with statistically significant: good and poor compliance had INR in the target range of 59.5 and 18.5 percent respectively, as follow ;

Group 1 ) Dose = 0.297 (body weight) + 0.180 (height) – 0.405 (age)

Group 2 ) Dose = - 0.608 (age) - 0.210 (compliance)

Conclusion and recommendations : The results of this study revealed that the factors associated with INR levels were medication adherence. For the new warfarin cases, the warfarin dosage prediction equation can be applied to calculate for the patient according to some conditions such as age, body weight, height, and medication adherence.