Clotblog with Dr Samuel Goldhaber

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INR testing in stable patients: Time to decrease frequency?

Mar 2, 2012 09:30 EST


Dr Sam Schulman's recent study calls into question the need to test INR every four weeks in stable patients. It's costly and perhaps unwarranted, as indicated by his data, which showed testing on a 12-week cycle to be noninferior to the standard practice. Is it now appropriate to consider relaxing the frequency of INR testing in this set of patients? What are your thoughts?

See also:

Schulman S, Parpia S, Stewart C, et al. Warfarin dose assessment every 4 weeks versus every 12 weeks in patients with stable international normalized ratios. Ann Intern Med 2011; 155:653-659. Available here.

Fewer INR checks safe in patients on stable-dose warfarin





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Your comments
INR testing in stable patients: Time to decrease frequency?
# 1 of 5
March 4, 2012 02:04 (EST)
Dr. Emmanuele Kouvoussis

I totally agree.

That's the way I treat my stable patients.

But how many are they in the end?

10% max. 
# 2 of 5
March 9, 2012 01:20 (EST)
Dr Canio Casale
I believe it would be completely correct to prolong the time per stable patients, and it coulld be started to be posponed at every two months(8 weeks),just to make sure that it works with the patients
# 3 of 5
March 12, 2012 08:33 (EDT)
WRW
Self testing once a week for patients who need to keep their INR 2.5-3.5 in the therapeutic range is a safer approach for me.
# 4 of 5
March 16, 2012 05:25 (EDT)
Dr JABeau

Each time INR is stable, i widen the interval between two INR tests, without overpassing 3 monthes. Like Dr E.K. 10% of my patients are checked every 3 monthes; most of them are tested every two monthes and 20% every month.

I noticed that INR is quite more stable when around 2 than when around 3.
# 5 of 5
March 27, 2012 05:12 (EDT)
Dr Kaushal Tiwari

I think this is a feasible option. Specially in developing countries, where patients either can’t afford the INR testing or INR testing is not available in their local healthcare setups. I have worked for sometime in Sudan and Nepal, where we used to check INR of our stable patients once in three months. Although, it was not motivated by any scientific evidence, but due to patients non compliance we had to do it. So, sometime patients non-compliance teaches you to treat them in other way, which could prove not bad, at the end. 

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Who's Talking
Samuel Z Goldhaber, MD
Professor of Medicine
Harvard Medical School
Director, Venous Thromboembolism Research Group
Co-Director, Anticoagulation Management Service
Cardiovascular Division
Brigham and Women's Hospital
Boston, MA