Skip to main content

Advertisement

SpringerLink
Log in

Health literacy and anticoagulation-related outcomes among patients taking warfarin

  • Original Articles
  • Published:
Journal of General Internal Medicine Aims and scope Submit manuscript

Abstract

BACKGROUND: Little is known about whether health literacy affects anticoagulation-related outcomes.

OBJECTIVE: To assess how health literacy is associated with warfarin knowledge, adherence, and warfarin control (measured by the international normalized ratio [INR]).

DESIGN: Survey.

PARTICIPANTS: Patients taking warfarin through an anticoagulation clinic.

MEASUREMENTS: Health literacy was measured using the short-form Test of Functional Health Literacy in Adults (s-TOFHLA), dichotomized as “limited” (score 0 to 22) and “adequate” (score 23 to 36). We asked patients to answer questions relating to their warfarin therapy and used multivariable logistic regression to assess whether health literacy was associated with incorrect answers. We also assessed whether health literacy was associated with nonadherence to warfarin as well as time in therapeutic INR range.

RESULTS: Bilingual research assistants administered the survey and s-TOFHLA to 179 anticoagulated English- or Spanish-speaking patients. Limited health literacy was associated with incorrect answers to questions on warfarin’s mechanism (adjusted odds ratio [OR] 4.8 [1.3 to 17.6]), side-effects (OR6.4 [2.3 to 18.0]), medication interactions (OR 2.5 [1.1 to 5.5]), and frequency of monitoring (OR 2.7 [1.1 to 6.7]), after adjusting for age, sex, race/ethnicity, education, cognitive impairment, and years on warfarin. However, limited health literacy was not significantly associated with missing warfarin doses in 3 months (OR 0.9 [0.4 to 2.0]) nor with the proportion of person-time in therapeutic INR range (OR 1.0 [0.7 to 1.4]).

CONCLUSIONS: Limited health literacy is associated with deficits in warfarin-related knowledge but not with self-reported adherence to warfarin or INR control. Efforts should concentrate on investigating alternative means of educating patients on the management and potential risks of anticoagulation.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  1. Ad Hoc Committee on Health Literacy for the Council on Scientific Affairs AMA Health literacy: report of the Council on Scientific Affairs. JAMA. 1999;281:552–7.

    Article  Google Scholar 

  2. Paasche-Orlow MK, Parker RM, Gazmararian JA, Nielsen-Bohlman LT, Rudd RR. The prevalence of limited health literacy. J Gen Intern Med. 2005;20:175–84.

    Article  PubMed  Google Scholar 

  3. Gazmararian JA, Baker DW, Williams MV, et al. Health literacy among Medicare enrollees in a managed care organization. JAMA. 1999;281:545–51.

    Article  PubMed  CAS  Google Scholar 

  4. DeWalt DA, Berkman ND, Sheridan S, Lohr KN, Pignone MP. Literacy and health outcomes. A systematic review of the literature. J Gen Intern Med. 2004;19:1228–39.

    Article  PubMed  Google Scholar 

  5. Kalichman SC, Benotsch E, Suarez T, et al. Health literacy and health-related knowledge among persons living with HIV/AIDS. Am J Prev Med. 2000;18:325–31.

    Article  PubMed  CAS  Google Scholar 

  6. Kalichman SC, Ramachandran B, Catz S. Adherence to combination antiretroviral therapies in HIV patients of low health literacy. J Gen Intern Med. 1999;14:267–73.

    Article  PubMed  CAS  Google Scholar 

  7. Wolf MS, Davis TC, Cross JT, et al. Health literacy and patient knowledge in a Southern US HIV clinic. Int J STD AIDS. 2004;15:747–52.

    Article  PubMed  CAS  Google Scholar 

  8. Kim SP, Knight SJ, Tomori C, et al. Health literacy and shared decision making for prostate cancer patients with low socioeconomic status. Cancer Invest. 2001;19:684–91.

    Article  PubMed  CAS  Google Scholar 

  9. Lindau ST, Tomori C, Lyons T, et al. The association of health literacy with cervical cancer prevention knowledge and health behaviors in a multiethnic cohort of women. Am J Obstet Gynecol. 2002;186:938–43.

    Article  PubMed  Google Scholar 

  10. Schillinger D, Grumbach K, Piette J, et al. Association of health literacy with diabetes outcomes. JAMA. 2002;288:475–82.

    Article  PubMed  Google Scholar 

  11. Levine MN, Raskob G, Beyth RJ, Kearon C, Schulman S. Hemorrhagic complications of anticoagulant treatment: the Seventh ACCP conference on antithrombotic and thrombolytic therapy. Chest. 2004;126(3 suppl):S287-S310.

    Article  Google Scholar 

  12. Chiquette E, Amato M, Bussey H. Comparison of an anticoagulation clinic with usual medical care. Arch Intern Med. 1998;158:1641–7.

    Article  PubMed  CAS  Google Scholar 

  13. Matchar DB, Samsa GP, Cohen SJ, Oddone EZ, Jurgelski AE. Improving the quality of anticoagulation of patients with atrial fibrillation in managed care organizations: results of the managing anticoagulation services trial. Am J Med. 2002;113:42–51.

    Article  PubMed  Google Scholar 

  14. Tang EO, Lai CS, Lee KK, et al. Relationship between patients’ warfarin knowledge and anticoagulation control. Ann Pharmacother. 2003;37:34–9.

    Article  PubMed  Google Scholar 

  15. Kagansky N, Knobler H, Rimon E, Ozer Z, Levy S. Safety of anticoagulation therapy in well-informed older patients. Arch Intern Med. 2004;164:2044–50.

    Article  PubMed  Google Scholar 

  16. Arnsten JH, Gelfand JM, Singer DE. Determinants of compliance with anticoagulation: a case-control study. Am J Med. 1997;103:11–7.

    Article  PubMed  CAS  Google Scholar 

  17. Waterman AD, Milligan PE, Bayer L, et al. Effect of warfarin nonadherence on control of the international normalized ratio. Am J Health-Syst Pharm. 2004;61:1258–64.

    PubMed  Google Scholar 

  18. Hylek E, Heiman H, Skates S, Sheehan M, Singer D. Acetaminophen and other risk factors for excessive warfarin anticoagulation. JAMA. 1998;279:657–62.

    Article  PubMed  CAS  Google Scholar 

  19. Schillinger D, Machtinger E, Wang F, et al. Medication mis-communication and anticoagulant care: are pictures worth more than words? In: Henriksen K, Battles J, Lewin DI, Marks E, eds. AHRQ Peer-Reviewed Publication: Advances in Patient Safety: from Research to Implementation, Vol. 2, Rockville, MD; 2005.

  20. Estrada CA, Hryniewicz MM, Higgs VB, Collins C, Byrd JC. Anticoagulant patient information material is written at high readability levels. Stroke. 2000;31:2966–70.

    PubMed  CAS  Google Scholar 

  21. Estrada CA, Martin-Hryniewicz M, Peek BT, Collins C, Byrd JC. Literacy and numeracy skills and anticoagulation control. Am J Med Sci. 2004;328:88–93.

    Article  PubMed  Google Scholar 

  22. McLaughlin GH. SMOG grading: a new readability formula. J Reading. 1969;12:639–46.

    Google Scholar 

  23. Teng EL, Hasegawa K, Homma A, et al. The Cognitive Abilities Screening Instrument (CASI): a practical test for cross-cultural epidemiological studies of dementia. Int Psychogeriatr. 1994;6:45–58.

    Article  PubMed  CAS  Google Scholar 

  24. Baker DW, Williams MV, Parker RM, Gazmararian JA, Nurss J. Development of a brief test to measure functional health literacy. Patient Educ Couns. 1999;38:33–42.

    Article  PubMed  CAS  Google Scholar 

  25. Williams MV, Parker RM, Baker DW, et al. Inadequate functional health literacy among patients at two public hospitals. JAMA. 1995;274:1677–82.

    Article  PubMed  CAS  Google Scholar 

  26. Man-Son-Hing M, Laupacis A, O’Connor A, et al. Warfarin for atrial fibrillation: the patient’s perspective. Arch Intern Med. 1996;156:1841–8.

    Article  PubMed  CAS  Google Scholar 

  27. Man-Son-Hing M, Laupacis A, O’Connor AM, et al. A patient decision aid regarding antithrombotic therapy for stroke prevention in atrial fibrillation: a randomized controlled trial. JAMA. 1999;282:737–43.

    Article  PubMed  CAS  Google Scholar 

  28. Chesney MA, Ickovics JR, Chambers DB, et al. Self-reported adherence to antiretroviral medications among participants in HIV clinical trials: the AACTG adherence instruments. patient care committee & adherence working group of the outcomes committee of the adult AIDS Clinical Trials Group (AACTG). AIDS Care. 2000;12:255–66.

    Article  PubMed  CAS  Google Scholar 

  29. Golin CE, Liu H, Hays RD, et al. A prospective study of predictors of adherence to combination antiretroviral medication. J Gen Intern Med. 2002;17:756–65.

    Article  PubMed  Google Scholar 

  30. Rosendaal FR, Cannegieter SC, van der Meer FJ, Briet E. A method to determine the optimal intensity of oral anticoagulant therapy. Thromb Haemost. 1993;69:236–39.

    PubMed  CAS  Google Scholar 

  31. Liang KY, Zeger SL. Longitudinal data analysis using generalized linear models. Biometrika. 1986;73.

  32. Schillinger D, Bindman A, Wang F, Stewart A, Piette J. Functional health literacy and the quality of physician-patient communication among diabetes patients. Patient Educ Couns. 2004;52:315–23.

    Article  PubMed  Google Scholar 

  33. Schillinger D, Piette J, Grumbach K, et al. Closing the loop: physician communication with diabetic patients who have low health literacy. Arch Intern Med. 2003;163:83–90.

    Article  PubMed  Google Scholar 

  34. Weiss BD, Coyne C. Communicating with patients who cannot read. N Engl J Med. 1997;337:272–4.

    Article  PubMed  CAS  Google Scholar 

  35. Cooper LA, Roter DL. Patient-provider communication: the effect of race and ethnicity on process and outcomes in health care. In: Smedley BD, Stith AY, Nelson AR, eds. Unequal Treatment: Confronting Racial and Ethnic Disparities in Health Care: A Report of the Institute of Medicine. Washington, DC: National Academy Press; 2002.

    Google Scholar 

  36. Rothman RL, DeWalt DA, Malone R, et al. Influence of patient literacy on the effectiveness of a primary care-based diabetes disease management program. JAMA. 2004;292:1711–6.

    Article  PubMed  CAS  Google Scholar 

  37. Schillinger D, Machtinger E, Wang F, Rodriguez M, Bindman A. Preventing medication errors in ambulatory care: the importance of establishing regimen concordance. In: Henriksen K, Battles J, Lewin DI, Marks E, eds. AHRQ Peer-Reviewed Publication: Advances in Patient Safety: From Research to Implementation, Vol. 2. Rockville, MD; 2005.

  38. Landefeld C, Rosenblatt M, Goldman L. Bleeding in outpatients treated with warfarin: relation to the prothrombin time and important remediable lesions. Am J Med. 1989;87:153–9.

    Article  PubMed  CAS  Google Scholar 

  39. Fang MC, Chang Y, Hylek EM, et al. Advanced age, anticoagulation intensity, and risk for intracranial hemorrhage among patients taking warfarin for atrial fibrillation. Ann Intern Med. 2004;141:745–52.

    PubMed  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Division of General Internal Medicine, University of California at San Francisco, San Francisco, CA, USA

    Margaret C. Fang MD, MPH & Edward L. Machtinger MD

  2. Primary Care Research Center, Department of Medicine, San Francisco General Hospital, University of California at San Francisco, San Francisco, CA, USA

    Frances Wang MS & Dean Schillinger MD

Authors
  1. Margaret C. Fang MD, MPH
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Edward L. Machtinger MD
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Frances Wang MS
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Dean Schillinger MD
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Margaret C. Fang MD, MPH.

Additional information

Preliminary results of this paper were presented during the 2004 Society of General Internal Medicine Annual meeting, Chicago, IL, USA.

The authors do not have any significant conflict of interests relating to this manuscript.

Dr. Schillinger was supported by an NIH Mentored Clinical Scientist Award K-23 RR16539-03 and an American Heart Association Junior Investigator Award. Electronic data were made available through the San Francisco General Hospital GCRC grant M01RR00083-42. Dr. Fang was supported by a Center for Aging in Diverse Communities award from the National Institute on Aging.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Fang, M.C., Machtinger, E.L., Wang, F. et al. Health literacy and anticoagulation-related outcomes among patients taking warfarin. J GEN INTERN MED 21, 841–846 (2006). https://doi.org/10.1111/j.1525-1497.2006.00537.x

Download citation

  • Issue Date:

  • DOI: https://doi.org/10.1111/j.1525-1497.2006.00537.x

Key words

Search

Navigation