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Home monitoring of INR using point-of-care testing is a viable option for patient involvement.

In 1998 I read about INR monitors to help me regulate my warfarin dose. Warfarin (Coumadin) is the only vitamin K antagonist (VKA) available in the US. I attempted to obtain one through my health insurance company.  It took two years and many letters from my Cardiologist to get my first monitor. Since that time most US insurance plans have reviewed the research data and have agreed to reimburse the cost of Monitors and supplies (test strips etc.). In March 2008 the largest Health Insurer (Medicare) began covering Monitors. As of April 2010 there are approximately 65,000 Americans who do self testing of the approximately 4 million Americans who take warfarin (1.6%). This is up from an estimated 50,000 in April of 2009. In some European Countries 25-50% of suitable patients on warfarin do self testing and self management.  In the US our health care system pits hospitals that want to fill beds against insurers that want to minimize reimbursement. In most European Countries health care providers and insurers are one and the same therefore reducing hospital admissions benefits and controls costs. Also in the US Insurance Companies pay health care clinicians very little to review weekly results for those patients who self-test. It is advantageous for providers to have patients come in for monthly INR testing.

In the US uncontrolled bleeding in patients on warfarin is estimated to lead to 43,000 Emergency visits and many deaths each year. A recent article by Long et al in the medical Journal “Thrombus” presents hospital admissions data from Duke University Health Systems (in North Carolina) from December 1, 2006-June 30, 2008 for anticoagulant adverse drug events (for abstract see: www.ncbi.nlm.nih.gov/pubmed/20167114. 169 events were identified with a median INR of 6.1 units.  Roughly half the adverse events were associated with bleeding.  The median length of hospital stay (LOS) was 4.8 days (range 0.8-82.7 days) with an associated hospital cost of $11,526 (US) (range $2,415-$170,302) per stay. Factors contributing to the hospital admissions for these adverse drug reactions (ADR's):

  • 1. Drug interactions particularly between antibiotics and warfarin.
  • 2. No documentation of a follow-up plan on the previous healthcare visit.
  • 3. Short duration of warfarin therapy.  36% of the patients with available records (42/116) were newly started on warfarin (less than 3 months) prior to the admission.

In their discussion Long et al report other US studies which confirm the high incidence of adverse events of anticoagulant medicines associated with emergency department (ED) visits and with ED visits resulting in hospitalization. The intensity of warfarin therapy is known to be strongly associated with bleeding risk, and an INR >4.5 is the single greatest risk factor for bleeding.

Long et al state that quality improvement in ambulatory care can prevent many of these adverse drug reactions associated with anticoagulant medicines.

They suggest:

  •  A. Strengthen the information technology (IT) infrastructure.  Ambulatory e-prescribing (electronic prescribing) to avoid drug interactions can help reduce medication errors. In addition Electronic Health Records (EHRs) can provide health care provider notes and medication records to assist monitoring patients and to document follow-up care.
  • B. Foster patient empowerment and engage patients in the ownership of their care.  Interactive health portals (personal health records) provide education and could permit patients to enter information, such as INR values or medication changes, to maintain an accurate, up-to-date health record.
  • C. Home monitoring of INR using point-of-care testing is a viable option for patient involvement.

The challenge to providers, to patients and to our health care system is enormous.

Michael Schwartz MD, USA (April 28th, 2010)