SPARCtool Notes

SPARCtool Notes

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What’s new in Version 10.1?

Who created SPARCtool?

Peter Loewen B.Sc.(Pharm), ACPR, Pharm.D., FCSHP, R.Ph.
Associate Professor | Faculty of Pharmaceutical Sciences
David H MacDonald Professor in Clinical Pharmacy
Faculty, Collaboration for Outcomes Research & Evaluation (CORE)
Researcher, UBC Center for Cardiovascular Innovation (CCI)
The University of British Columbia | Vancouver Campus
2405 Wesbrook Mall | Vancouver, BC Canada V6T 1Z3 | profile

Dr. Loewen has no financial or other conflicts of interest related to SPARCtool or the stroke prevention therapy options it does or does not include.

Where do the stroke risk estimates come from?

I read a different paper about CHADS2 or CHA2DS2-VASc and it shows different numbers than SPARCtool. Why?

Every validation study will produce different numbers for thromboembolism risk in every stratum of CHADS2 or CHA2DS2-VASc score. This is called the “calibration” of the prediciton model. The better the model, the more consistent the estimates will be between cohorts studied (i.e., better calibration). SPARCtool uses data from what is currently the largest and longest-term evaluation of the scores (see above).

HAS-BLED bleeding risk estimation

Where do the efficacy and bleeding risks of the antithrombotic therapies come from?

How is the risk of major bleeding on “no therapy” derived?

This is patient-specific based on sex and age from the “baseline cohort” in Selak et al. JAMA. 2018;319(24):2507–2520. SPARCtool uses age>60 vs. age<60 from this study.

What about paroxysmal (intermittent) atrial fibrillation?

No trials of efficacy of antithrombotic therapy in patients with paroxysmal atrial fibrillation have been conducted. All major consensus guidelines suggest treating similarly to permanent/persistent/chronic atrial fibrillation. In reality, evidence here and here indicates stroke risk is probably somewhat proportional to the amount of time the patient is actually in AF, up to the maximums estimated by CHADS2/CHA2DS2-VASc.

Can these ANNUAL risks of stroke (or bleeding) be added together to estimate longer-term risks?

Not directly, but they can be used to estimate longer-term risk. If the annual risk of stroke or bleeding were constant over time (which they are not… they generally go up as age and other risk diagnoses accumulate), the formula to estimate the risk of a an event after t years is:

cumulative probabiliy of event = 1-[(1-annual probability of event)^ t]
e.g.  in a patient with 15% annual SSE risk, their probabiliy of having an SSE by the end of year 3 is 1-[(1-0.15)exp(3)] = 39%

Because of the above, in the absence of treatment changes, these will be underestimates of risk.

Renal dysfunction

Why does SPARCtool extend the HAS-BLED bleeding risk to dabigatran, rivaroxaban, apixaban, and edoxaban?

I believe this is reasonable for two reasons: (1) Head-to-head trials so far show major bleeding risk to be similar between warfarin and new oral anticoagulants (RE-LY, ROCKET-AF, ARISTOTLE) and (2) HAS-BLED was validated in a population which included both warfarin and ximelagatran patients in the SPORTIF trials.

Has this system been evaluated in clinical practice?

Yes, in various forms:

Release Notes

version 10.1 release notes (October 2022)

Updated efficacy estimate for edoxaban 60mg to 13% RRR vs. warfarin per ENGAGE-AF superiority analysis. Brings the efficacy estimate method into line with that of the other DOACs where the superiority analysis was statistically significant (dabigatran 150mg, apixaban).

version 10 release notes (October 2022)

SPARCtool & SPARCmobile

version 9 release notes (June 2019)



version 8.2 release notes (Sept 2017)



version 8.1 release notes (June 2016)


version 8 release notes (June 2016)



version 7 release notes (January 2015)



version 6.21 release notes (April 2013)



version 6.1 release notes (March 2013)