Effect of PST on Warfarin Management and Major Clinical Outcomes
By: Alere Staff
The world’s largest meta-analysis of patient self testing (PST) found a significant reduction in death (26%) and major thrombosis (42%) over usual anticoagulation care with no increase in major bleeding events. The study, Effect of Patient Self testing and Self management of Long Term Anticoagulation, evaluated 22 random controlled trials conducted over 44 years and included 8,413 patients.1 The findings were published in the April 2011 issue of Annals of Internal Medicine.1 The results were similar to the 2006 meta-analysis of patient self testing for patients on warfarin published in the British medical journal Lancet.
Five of the twenty-two trials included only PST while fourteen evaluated PSM. The remaining trials were between PST and PSM. The average age was 65 years old and 75% were men. “Control groups”, also called “usual clinic care” were most commonly found in anticoagulation clinics (11 trials) or in primary care and physician’s offices (7 trials). The THINRS VA Cooperative Studies trial was included in the Annals evaluation and added additional strength to the study findings.
“The pooled weighted time in target range (TTR) mean was 71% (range of means, 43-87%) in the PST or PSM group and 59% (range of means 22%-78%) in the usual care group. 50% of the trials (11/22) observed weekly home INR testing with the remaining trials found either variable testing frequencies or other than weekly.1
Strength of Medical Evidence
14 of the 22 trials included “moderate” strength level of evidence to evaluate major thrombosis events. 16 of the 22 trials included “moderate” strength of evidence on major bleeding events while 13 trials included mortality data with “low” strength of evidence.
Thrombosis, Bleeding, Mortality Outcomes
A reduction of 42% major thrombosis was found in patients randomly assigned in the PST or PSM groups. There were 7,759 patients included in the analysis of thrombosis between PST or PSM and usual care. No additional major bleeding was observed in PST or PSM studies when compared with usual clinic care. The combined studies found a 26% reduction in death in the PST or PSM group but the strength of evidence was reported to be low.1
Lead author Bloomfield, MD noted the mechanisms by which PST or PSM led to reductions is thromboembolic events and reduced bleeding events is believed to be associated with higher proportions of time in target range which is achieved by more frequent testing and dosing adjustments. This in turn leads to an increased quality of anticoagulation control.1
The studies supported careful patient selection remains critical to successful patients self testing. In most of the 22 trials, 50% or fewer patients met eligibility requirements for PST enrollment.The THINRS trial was the exception where >80% of patients were successful in patient self testing. A suitable patient was defined as: willing and motivated, confidence in their ability, and able to overcome their perceived physical inability.1 Patients not physically able to perform the finger-stick test often use a caregiver to perform the test. Self testing can reduce death and risk of thromboembolic events for those on long-term anticoagulation who meet the aforementioned criteria.1
- Bloomfield, H. Meta-analysis of patient self testing and self management of long-term anticoagulation on major clinical outcomes. Annals of Internal Medicine. 2011. 154; 472-482.