Assessment of Outpatients' Knowledge and Adherence on Warfarin: The Impact of a Simple Educational Pamphlet

Document Type : Research article

Authors

1 Rajaei Cardiovascular, Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran.

2 Department of Clinical Pharmacy, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

3 Chronic Respiratory Diseases Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran.

4 Food Safety Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

Abstract

Warfarin is a critical medication that is broadly used for the treatment and prevention of
thromboembolic disorders. Due to warfarin’s narrow therapeutic index, it is crucial that patients
follow an appropriate dosage regimen. Patient knowledge is one of the most important factors
to safe and effective use of warfarin. Due to the obvious risks of anticoagulants administration,
evaluating patients’ awareness seems to be crucial. The purpose of this article was to evaluate
the effects of intervention by an informative pamphlet on knowledge and adherence of patients
who consumed warfarin. Two-hundred and fifty patients receiving warfarin were assigned to
the study. They were asked to fill in the questionnaire. Then patients were provided with an
educational pamphlet. In the second interview, patients filled the questionnaire again. Obtained
data were assessed and analyzed by Excel software and SPSS version 18.0. Out of 250 patients
who entered the study, 150 patients attended for the second interview. Data analysis revealed
that out of 13 explanatory factors, only patients’ literacy level and income were the predictors
which inversely correlated with the patients’ adherence (r = -0.44; p = 0.00040). Our educational
intervention had a positive impact on patients’ knowledge regarding anticoagulation (p < 0.0001).
Our findings revealed that a written informative pamphlet could effectively increase patients’
anticoagulation knowledge. Since, poorly literate patients had a lesser level of knowledge
before and after educational intervention, it is recommended to develop appropriate educational
programs especially designed for this group of patients.

Keywords

Main Subjects


(1) Kimmel SE, Chen Z, Price M, Parker CS, Metlay JP,
Christie JD, Brensinger CM, Newcomb CW, Samaha
FF and Gross R. The influence of patient adherence
on anticoagulation control with warfarin: results
from the international normalized ratioadherence
and genetics (IN-RANGE) study. Arch. Intern. Med.
(2007) 167: 229-35.
(2) Harter K, Levine M and Henderson SO.
Anticoagulation drug therapy: a review. West. J.
Emerg. Med. (2015) 16: 11-7.
(3) Pirmohamed M. Warfarin: almost 60 years old
and still causing problems. Br. J. Clin. Pharmacol.
(2006) 62: 509-11.
(4) Schein JR, White CM, Nelson WW, Kluger J,
Mearns ES and Coleman CI. Vitamin K antagonist
use: evidence of the difficulty of achieving and
maintaining target INR range and subsequent
consequences. Thromb. J. (2016) 14: 14.
(5) Nasser S, Mullan J and Bajorek B. Challenges of
older patients’ knowledge about warfarin therapy. J.
Prim. Care Community Health (2011) 3: 65-74.
(6) Kumar S, Haigh JR, Rhodes LE, Peaker S, Davies
JA, Roberts BE and Feely MP. Poor compliance
is a major factor in unstable outpatient control of
anticoagulant therapy. Thromb. Haemost. (1989) 62:
729-32.
(7) Bajorek BV, Ogle SJ, Duguid MJ, Shenfield GM and
Krass I. Management of warfarin in atrial fibrillation:
views of health professionals, older patients and
their carers. Med. J. Aust. (2007) 186: 175-80.
(8) Clarkesmith DE, Pattison HM, Lip GYH and
Lane DA. Educational intervention improves
anticoagulation control in atrial fibrillation patients:
the TREAT randomised trial. PLoS One (2013) 8:
e74037.
(9) Abbasinazari M, Farsad BF, Dabagh A and
Bakshandeh H. Evaluation of time in therapeutic
range (TTR) in patients with non-valvular atrial 
320
Fariborz Farsad B et al. / IJPR (2019), 18 (Special Issue): 315-320
fibrillation receiving treatment with warfarin in
Tehran, Iran: A cross-sectional study. J. Clin. Diagn.
Res. (2016) 10: FC04-6.
(10) Ansell J, Hirsh J, Poller L, Bussey H, Jacobson A
and Hylek E. The pharmacology and management
of the vitamin K antagonists: the seventh ACCP
conference on antithrombotic and thrombolytic
therapy. Chest (2004) 126 (3 Suppl): 204S-33S.
(11) Parmenter K and Wardle J. Development of a
general nutrition knowledge questionnaire for
adults. Eur. J. Clin. Nutr. (1999) 53: 298-308.
(12) Allen RM and Jones MP. The validity and
reliability of an asthma knowledge questionnaire
used in the evaluation of a group asthma education
self-management program for adults with asthma.
J. Asthma (1998) 35: 537-45.
(13) Haladyna TM, Downing SM and Rodriguez MC. A
review of multiple-choice item-writing guidelines
for classroom assessment. Appl. Meas. Educ.
(2002) 15: 309-34.
(14) Wild D, Grove A, Martin M, Eremenco S, Mcelroy
S, Verjee-lorenz A and Erikson P. Principles of
good practice for the translation and cultural
adaptation process for patient-reported outcomes
(PRO) measures: report of the ISPOR task force
for translation and cultural adaptation. Value
Health (2005) 8: 94–104.
(15) Matalaqah LM, Radaideh K and Hassali MA. An
instrument to measure anticoagulation knowledge
among Malaysian community: A translation
and validation study of the oral anticoagulation
knowledge (OAK) test. Asian J. Biomed. Pharm.
Sci. (2013) 3: 30-7.
(16) Fang MC, Machtinger EL, Wang F and Schillinger
D. Health literacy and anticoagulation-related
outcomes among patients taking warfarin. J. Gen.
Intern. Med. (2006) 21: 841-6.
(17) Ad Hoc Committee on Health Literacy for the
Council on Scientific Affairs, American Medical
Association. Health Literacy: Report of the Council
on Scientific Affairs. JAMA (1999) 281: 552-7.
(18) Jin J, Sklar GE, Min Sen Oh V and Chuen Li S.
Factors affecting therapeutic compliance: A review
from the patient’s perspective. Ther. Clin. Risk
Manag. (2008) 4: 269-86.
(19) Senior V, Marteau TM and Weinman J. Self-reported
adherence to cholesterol-lowering medication in
patients with familial hypercholesterolaemia: the
role of illness perceptions. Cardiovasc. Drugs
Ther. (2004) 18: 475-81.
(20) Rothman RL, DeWalt DA, Malone R, Bryant B,
Shintani A, Crigler B, Weinberger M and Pignone
M. Influence of patient literacy on the effectiveness
of a primary care-based diabetes disease
management program. JAMA (2004) 292: 1711-6.
(21) Rolls CA, Obamiro KO, Chalmers L and Bereznicki
LRE. The relationship between knowledge, health
literacy, and adherence among patients taking oral
anticoagulants for stroke thromboprophylaxis in
atrial fibrillation. Cardiovasc. Ther. (2017) 35:
e12304.
(22) Hu A, Chow CM, Dao D, Errett L and Keith M.
Factors influencing patient knowledge of warfarin
therapy after mechanical heart valve replacement.
J. Cardiovasc. Nurs. (2006) 21: 176-7.
(23) Estrada CA, Martin-Hryniewicz M, Peek BT,
Collins C and Byrd JC. Literacy and numeracy
skills and anticoagulation control. Am. J. Med. Sci.
(2004) 328: 88-93.
(24) Schillinger D, Machtinger E, Wang F, Rodriguez M
and Bindman A. Preventing Medication Errors in
Ambulatory Care: The Importance of Establishing
Regimen Concordance. In: Henriksen K, Battles
JB and Marks ES. (eds.) Advances in Patient
Safety: From Research to Implementation. (Volume
1: Research Findings). Agency for Healthcare
Research and Quality, Rockville (2005) 206-8.
(25) Uygungül E, Ayrik C, Narci H, Erdoğan S, Toker İ,
Demir F and Karaaslan U. Determining risk factors
of bleeding in patients on warfarin treatment. Adv.
Hematol. (2014) 2014: 369084.
(26) Makohusová M, Mrázová V, Bednárová A,
Milatová E, Sokol J, Pleško M and Bátorovád A.
Comparison of two different techniques of warfarin
dosing determination - A chemometrics study. Iran.
J. Pharm. Res. (2019) 18: 1010-9.