Elevated matrix metalloproteinase-9 (MMP-9) levels are associated with an increased risk for hemorrhagic transformation (HT) following acute ischemic stroke, according to study findings published in Neurology Open Access.Researchers conducted a systematic review and meta-analysis to evaluate the association between MMP levels and hemorrhagic complications after ischemic stroke. Eligible studies included primary research evaluating MMP levels in relation to HT outcomes, with cohort and case-control studies included.

The primary outcome was the association between MMP levels and HT occurrence, while secondary analyses evaluated diagnostic performance measures, including sensitivity and specificity. Statistical analyses included pooled mean differences for continuous outcomes and diagnostic test accuracy modeling.

 

These findings support the biological relevance of MMP-9 as a marker of [blood-brain barrier] disruption and vascular injury.

The meta-analysis included 9 studies encompassing 1051 patients. Among these, 274 patients experienced HT and 777 did not. Across studies, patient ages ranged from 60 to 90 years overall, and study populations included patients receiving thrombolysis, anticoagulation, and endovascular therapies. MMP-9 levels were measured at varying time points, including at admission, baseline, within 24 to 36 hours after admission, and before or after endovascular thrombectomy procedures.

MMP-9 levels were significantly higher among patients who developed HT compared with those who did not, with a pooled mean difference of 70.51 ng/mL (95% CI, 35.47-105.5). Although this analysis demonstrated substantial heterogeneity across studies (I² =93%), diagnostic accuracy analyses showed more consistent performance. Pooled sensitivity and specificity for MMPs were 0.79 (95% CI, 0.79-0.84) and 0.796 (95% CI, 0.67-0.88), respectively. The positive likelihood ratio was 3.88 (95% CI, 2.35-6.40), and the negative likelihood ratio was 0.26 (95% CI, 0.20-0.35), corresponding to a diagnostic odds ratio of 14.75 (95% CI, 7.62-28.58).

Across individual studies, sensitivity estimates ranged from approximately 0.72 to 0.87, while specificity values varied from 0.75 to 0.90. The pooled diagnostic accuracy estimates demonstrated consistent performance across studies, supporting the potential role of MMP-9 in risk stratification for hemorrhagic complications after ischemic stroke.

The biological role of MMP-9 in degrading extracellular matrix components and disrupting the blood-brain barrier may explain its association with HT, as elevated levels reflect ongoing vascular injury and inflammation.Study limitations include variability in MMP-9 measurement timing, lack of standardized cutoff thresholds, differences in treatment protocols, heterogeneous study designs, variability in HT classification methods, and limited reporting on symptomatic vs asymptomatic HT, all of which may affect generalizability and clinical implementation.

“These findings support the biological relevance of MMP-9 as a marker of [blood-brain barrier] disruption and vascular injury,” the study authors concluded.