Predictive factors for obtaining a correct therapeutic range using antivitamin K anticoagulants: a tertiary center experience of patient adherence to anticoagulant therapy

Abstract

Background

Patient adherence is an essential factor in obtaining efficient oral anticoagulation using vitamin K antagonists (VKAs), a situation with a narrow therapeutic window. Therefore, patient education and awareness are crucial for good management. Auditing the current situation would help to identify the magnitude of the problem and to build tailored education programs for these patients.

Methods

This study included 68 hospitalized chronically anticoagulated patients (mean age 62.6±13.1 years; males, 46%) who responded to a 26-item questionnaire to assess their knowledge on VKA therapy management. Laboratory and clinical data were used to determine the international normalized ratio (INR) at admission, as well as to calculate CHA₂DS₂-VASC and HAS-BLED scores for patients with atrial fibrillation.

Results

The majority of patients (62%) were receiving VKA for atrial fibrillation, the others for a mechanical prosthesis and previous thromboembolic disease or stroke. In the atrial fibrillation group, the mean CHA₂DS₂-VASC score was 3.1±1.5, while the average HAS-BLED score was 1.8±1.2. More than half of the patients (53%) had an INR outside of the therapeutic range at admission, with the majority (43%) having a low INR. A correct INR value was predicted by education level (higher education) and the diagnostic indication (patients with mechanical prosthesis being best managed). Patients presenting with a therapeutic INR had a trend toward longer treatment duration than those outside the therapeutic range (62±72 months versus 36±35 months, respectively, P=0.06). There was no correlation between INR at admission and the patient’s living conditions, INR monitoring frequency, and bleeding history.

Conclusion

In a tertiary cardiology center, more than half of patients receiving VKAs are admitted with an INR falling outside the therapeutic range, irrespective of the bleeding or embolic risk. Patients with a mechanical prosthesis and complex antithrombotic regimens appear to be the most careful with INR monitoring, especially if they have a higher level of education. Identifying patient groups with the lowest time interval spent in the therapeutic range could help attending physicians educate patients focusing on specific awareness issues.

Keywords:

• anticoagulant therapy
• antivitamin K agents
• patient adherence
• questionnaire

Supplementary material

Patient awareness questionnaire

Surname:

Forename:

Sex: M/F           Age:

1. The diagnosis for which ACT was prescribed was:

   1. Deep VT

   2. PTE

   3. Superficial VT

   4. Atrial fibrillation (paroxysmal, persistent, permanent)

   5. Cardiac valve prosthesis: metallic/biological

   6. Stroke

   7. Cardiac ischemic disease (what type: ..........................................................................................................................)

   8. Cardiac failure with low EF (most recent EF being ...............................................................................................)

   9. Left ventricular aneurysm

   10. Other .................................................................................

2. Level of education:

   1. None

   2. Primary school

   3. Secondary school

   4. High school

   5. Bachelor or above

3. Living environment:

   1. Rural

   2. Urban

4. Where was ACT prescribed?

   1. Ambulatory clinic

   2. Hospital

   3. General practitioner’s office

   4. Home consultation-visit

5. Who prescribed the ACT?

   1. Cardiologist

   2. Internal medicine doctor

   3. Neurologist

   4. General practitioner

   5. Other ................................................................................................................................................................................

6. What AC drug do you use?

   1. Sintrom

   2. Trombostop

   3. Other ..................................................................................

7. Do you use any other antithrombotic drug?

   1. Aspirin; dosage .........................................................................

   2. Plavix (or other brand names for clopidogrel):

   3. Dosage........................................................................................

   4. Other.........................................................................................

8. Were you informed about the benefits of ACT?

   1. Yes

   2. No

9. Were you informed about the risks of ACT?

   1. Yes

   2. No

10. How long have you been under ACT?

    ............................................... (years and months)

11. For how long have you been informed the duration of ACT is, in your case?

    1. The whole life

    2. For limited period of time ..............................................................................................

12. I haven’t been informed about the duration

    1. Who administers the therapy for you?

    2. I do it myself

    3. A member of the family

    4. Somebody else

13. Do you know your current ACT daily dosage that you have been prescribed?

    1. Yes

    2. No

14. Do you follow this daily dosage?

    1. Yes

    2. No

    3. Only sometimes

15. What is the correct INR interval when undergoing ACT?

    1. 1.5–2

    2. 2–3

    3. 2.5–3

    4. 3–3.5

    5. 3.5–4

    6. I don’t know

    7. I haven’t been told

16. What is the time interval after which you were informed to repeat your INR dosing?

    1. Once a week

    2. Less than once a month (how many times per months...............................................................................................?)

    3. Once a month

    4. Once every 2 months

    5. More than once every 2 months

    6. I don’t know

    7. I haven’t been told

17. What is the time interval after which you repeat your INR dosing?

    1. Once a week

    2. Less than once a month (how many times per months..................................................................................................?)

    3. Once a month

    4. Once every 2 months

    5. More than once every 2 months

    6. I don’t know

    7. It’s not a set time interval

18. (If you answered d, e, f, and g at question 17) Why do you repeat the INR dosing after longer time intervals?

    1. Financial reasons

    2. The long distance between where I live and the nearest laboratory

    3. I forgot my ACT dosage

    4. I don’t consider it to be important

19. Who adjusts your ACT dosage after the INR analysis, if needed?

    1. Cardiologist

    2. Internal medicine doctor

    3. Neurologist

    4. General practitioner

    5. Other..................................................................................

    6. I adjust it myself

20. What were you told the emergency INR is?

    1. Over 3

    2. Over 4

    3. Over 5

    4. Over 6

    5. I don’t know

21. Have you heard of devices for INR monitoring at home?

    1. Yes

    2. No

22. Do you own such a device?

    1. Yes

    2. No

23. Have you had any hemorrhage in the time you have been undergoing ACT?

    1. Yes

    2. No

24. If yes, what type of hemorrhage have you had?

    1. Epistaxis

    2. Digestive hemorrhage (red blood in the stool; black color stools; vomiting of red blood or blood clots)

    3. Hematuria

    4. Hematoma

    5. Other...........................................................................................................................................................................

25. Do you know the INR value at the moment of the hemorrhage?....................................................................................................................................................................................

26. If you could choose between more AC drugs what would be the determining factor?

    1. The longer period for INR dosing (or never having to do it at all)

    2. The price of the drug

    3. The safety of the drug

INR on current admission:

For atrial fibrillation:

CHA₂DS₂-VASc: HAS-BLED:

Other comments:

Abbreviations
ACT	=	anticoagulant therapy
AC	=	anticoagulant
EF	=	ejection fraction
INR	=	international normalized ratio
PTE	=	pulmonary thromboembolism
VT	=	venous thrombosis

Disclosure

The authors report no conflicts of interest in this work.