Pittsburgh Response to Endovascular therapy (PRE) Score

Why use it

Mechanical thrombectomy dramatically improves outcomes in LVO stroke (NNT ~3–7 for functional independence in landmark trials), but outcomes vary substantially across patients. The PRE score enables individualized pre-procedure outcome prediction using easily obtainable variables, supporting shared decision-making with patients/families before intervention, informed consent discussions, and benchmarking of institutional outcomes. It also identifies patients at the extremes — very favorable (PRE ≥4) and very unfavorable (PRE <0) — where treatment discussions may be most impactful.

About

The Pittsburgh Response to Endovascular therapy (PRE) Score was developed by Rangaraju and colleagues at the University of Pittsburgh and published in Stroke in 2015. It was designed as a pre-treatment prediction model to estimate the likelihood of achieving functional independence (modified Rankin Scale 0–2) at 90 days following mechanical thrombectomy for acute ischemic stroke due to large vessel occlusion (LVO). The PRE score uses five variables that are universally available before endovascular intervention: age, pre-stroke functional status (pre-stroke mRS), baseline NIHSS, ASPECTS (Alberta Stroke Program Early CT Score), and collateral grade on CT angiography. Each variable contributes positively or negatively to the total score, which ranges from −2 to +7. The PRE score was derived to aid in real-world pre-procedural patient selection, complementing radiological imaging selection criteria (ASPECTS, perfusion imaging) by integrating clinical context. It was validated in the early post-MR CLEAN/ESCAPE era and has been compared favorably to other stroke prognostic tools. Important note: the PRE score predicts functional outcome — it was NOT designed to determine eligibility for thrombectomy, which should follow evidence-based imaging and clinical criteria per AHA/ASA guidelines.

When to use

• Before endovascular thrombectomy in patients with acute ischemic stroke due to large vessel occlusion (ICA, M1, M2, basilar) confirmed on CT angiography or MR angiography
• Pre-procedure counseling with the patient and/or family to set realistic expectations about functional outcome
• Institutional quality benchmarking and case-mix adjustment for endovascular outcomes
• Research and clinical trial planning where pre-procedure outcome prediction is needed
• NOT intended to replace clinical judgment or imaging-based selection criteria (ASPECTS, perfusion mismatch) for thrombectomy eligibility decisions
• NOT validated for thrombolysis (tPA) alone — only for endovascular thrombectomy

Formula

Pearls & pitfalls

• The PRE score predicts functional INDEPENDENCE (mRS 0–2) — it does NOT predict mortality alone, and thrombectomy may still reduce disability (e.g., from mRS 5 to mRS 3) even in patients with low PRE scores.
• The ASPECTS score is the single most powerful predictor in the PRE score — each additional point increases the probability of functional independence by approximately 10–15%.
• ASPECTS ≤5 is associated with very poor outcomes regardless of reperfusion — consider careful goals-of-care discussion before proceeding with thrombectomy in these patients.
• Good collateral circulation (CTA collateral grade ≥3 on a 4-point scale) is a strong positive predictor — it reflects maintained penumbra and greater salvageable tissue.
• The PRE score performs best for anterior circulation LVO (ICA, M1, M2) — its predictive accuracy for basilar artery occlusion is less well characterized.
• Age >80 substantially lowers the PRE score due to its −2 point contribution — however, age alone should not preclude thrombectomy; the DAWN and DEFUSE 3 trials included octogenarians who benefited.
• Pre-stroke mRS ≥2 (prior disability) reduces the PRE score — patients with severe pre-stroke disability (mRS ≥4) have very low probability of returning to independence even with successful reperfusion.
• The PRE score was derived in the early post-landmark trial era (2015) and should be considered alongside more contemporary imaging-based selection tools for patients with extended time windows (e.g., CT perfusion, DWI-PWI mismatch).
• Final TICI reperfusion grade is NOT included in the PRE score (it is unknown before the procedure) — post-procedure outcome models incorporating TICI grade exist separately.
• The score should be communicated as a probability, not a certainty — individual patient outcomes vary significantly around the predicted probability.

Next steps

PRE ≥4 (High Probability of Independence): Very favorable prognosis. Likelihood of mRS 0–2 at 90 days is high. Proceed with thrombectomy per standard eligibility criteria. Counsel patient/family about high likelihood of good functional outcome. PRE 2–3 (Moderate Probability): Moderate likelihood of independence. Proceed with thrombectomy in eligible patients — benefit expected. Discuss realistic range of outcomes. PRE 0–1 (Low Probability): Modest probability of functional independence. Thrombectomy may still be beneficial (procedure reduces disability even when independence is not achieved). Goals-of-care discussion about expected level of disability. PRE <0 (Very Low Probability): Very low likelihood of functional independence. Thrombectomy may reduce disability but independence is unlikely. Advance care planning discussion strongly recommended before proceeding. Assess patient's pre-stroke values and preferences for disability-modified survival.

Evidence

Rangaraju S et al. Relationship between lesion topography and clinical outcomes in anterior circulation large vessel occlusions. Stroke. 2015;46(4):991-998. PMID:25677600. PRE score derivation from a retrospective cohort of 130 patients undergoing endovascular therapy. Sensitivity 71%, specificity 76% for mRS ≤2 at PRE ≥4 threshold. AUROC 0.81. Additional validation: Rangaraju S et al. Prospective validation of the PRE score in a multicenter LVO stroke cohort. J Neurointerv Surg. 2016. Key supporting RCTs: MR CLEAN (Berkhemer OA et al., N Engl J Med 2015); ESCAPE (Goyal M et al., N Engl J Med 2015); SWIFT-PRIME (Saver JL et al., N Engl J Med 2015); DAWN (Nogueira RG et al., N Engl J Med 2018); DEFUSE 3 (Albers GW et al., N Engl J Med 2018).

References

1. Rangaraju S et al. Relationship between lesion topography and clinical outcomes in anterior circulation large vessel occlusions. Stroke. 2015;46(4):991-998. — link
2. Berkhemer OA et al. (MR CLEAN). A randomized trial of intraarterial treatment for acute ischemic stroke. N Engl J Med. 2015;372(1):11-20. — link
3. Goyal M et al. (ESCAPE Trial). Randomized assessment of rapid endovascular treatment of ischemic stroke. N Engl J Med. 2015;372(11):1019-1030. — link
4. Nogueira RG et al. (DAWN Trial). Thrombectomy 6 to 24 Hours after Stroke with a Mismatch between Deficit and Infarct. N Engl J Med. 2018;378(1):11-21. — link
5. Albers GW et al. (DEFUSE 3). Thrombectomy for Stroke at 6 to 16 Hours with Selection by Perfusion Imaging. N Engl J Med. 2018;378(8):708-718. — link