Home anticoagulant monitoring matches in-clinic testing

19 November 2008

MedWire News: Weekly self-monitoring of warfarin therapy is an effective alternative to monthly evaluation in a high-quality anticoagulation clinic, the primary findings of The Home INR Study (THINRS) suggest.

Although the trial did not meet its primary endpoint of improvement in the time to a first major event (stroke, major bleed, or death) with point-of-care testing, the study did show that patients who monitored their international normalized ratio (INR) every week at home spent more time in the target range than those who were monitored in the clinic once a month.

Importantly, 80% of patients successfully demonstrated that they could monitor their INRs at home, with or without the aid of a healthcare advisor, and that they were more satisfied with their treatment overall.

“These results support that home testing is an acceptable alternative to high-quality clinic care,” said presenting author Alan Jacobson, of Loma Linda University in California, USA.

Jacobsen added that home testing may be preferable for certain patients, such as those for whom regular follow-up in the clinic may be difficult due to reasons of disability or distance.

The study findings were presented at the final late-breaking clinical trials session at the 2008 American Heart Association Scientific Sessions held in New Orleans, Louisiana, USA.

THINRS involved 2922 randomized patients who required long-term anticoagulant therapy with warfarin and were being treated at 28 Veteran’s Affairs medical centers in the USA. The majority (98%) of patients was therefore male and had a mean age of 67 years. Most (~80%) had atrial fibrillation, with around one quarter with a mechanical heart valve. One third of patients had concomitant diabetes and around 10% had suffered a previous stroke.

After an initial training period lasting 2–4 weeks, patients who had proved competent at using the hand-held INR monitors were randomized into the main part of the study. The 1465 patients who were randomly assigned to continue with self-testing used the home INR monitor once a week and telephoned their INR readings into a central reporting system. They were instructed to call the clinic if their INR fell outside their target range. The remaining 1457 patients visited a specialist anticoagulant clinic once a month for INR measurement.

Over the 3-year study period, 6.2% of patients using home INR monitoring and 6.9% of those who underwent monthly in-clinic INR testing experienced a first major event (hazard ratio=0.868).

There was no difference between the groups in terms of the individual event outcomes: the stroke rate was 0.69% per patient-years in the home monitoring group and 0.76% in the clinic-assessed group. Rates of major bleed were 3.85% and 4.46% per patient-years, respectively, and the death rates were 3.38% and 3.71% per patient-years.

Commenting on the study, Alan Go, of Kaiser Permanente of Northern California in Oakland, USA, said: “THINRS has reinforced the message that delivering high quality anticoagulation therapy, regardless of the approach, leads to low rates of ischemic stroke and intracranial hemorrhage in patients with atrial fibrillation or mechanical heart valves.”

American Heart Association Scientific Sessions; New Orleans, Louisiana, USA: 8–12 November 2008