OBJECTIVESHemorrhagic transformation (HT) is a complication occurring in patients with acute ischemic stroke (AIS) either spontaneously or post-thrombolysis leading to significant morbidity and mortality. We assessed circulating matrix metalloproteinase-9 (MMP-9), Claudin-5, and soluble serum stimulation-2 (sST2) in HT and stroke severity in AIS based on their temporal distribution.MATERIALS AND METHODSWe prospectively enrolled 111 AIS patients within 12 h from onset. Patient demographic, clinical, and imaging details were documented. Follow-up imaging was conducted 24-48 h after admission. Blood samples were taken at three time-points from stroke onset. HT was classified according to the European Co-operative Acute Stroke Study-III(ECASS-III). Stroke severity was assessed using the National Institutes of Health Stroke Scale (NIHSS). Multiple logistic regression and receiver operating characteristic curve were conducted to determine the discriminative capacity.RESULTSMean age was 62.3 ± 11.7 years and median baseline NIHSS was 12[IQR 8.0-18.0]. HT was detected in 30(27%) patients. Biomarker levels at 12 h were elevated with median MMP-9 concentration of 153.9 ng/mL[IQR 110.6-309 ng/mL] indicating a trend toward significant positive correlation with HT(P = 0.05). Claudin-5 levels at 12 h was elevated but was not statistically significant (43.1 pg/mL[IQR:26.7-72.6 pg/mL] vs 59.4 pg/mL[IQR:24.5-100.8 pg/mL];P = 0.4). Multiple logistic regression indicated Claudin-5 levels at 12 h (OR 9.46;95% CI:1.97-64.6;P = 0.010) and baseline low ASPECTS score(OR 20.3;95% CI:3.46-193; P = 0.003) independently predicted HT. MMP-9 at 12 h was significantly elevated in patients with moderate to severe strokes (P = 0.04).CONCLUSIONSClaudin-5 and low ASPECTS independently predicted HT. MMP-9 was positively correlated with baseline stroke severity.