Possible Influence of Ethnicity on Computed Tomography Perfusion Parameter Thresholds in Acute Ischaemic Stroke

Introduction: Tissue at risk, as estimated by CT perfusion utilizing T_max+6, correlates with final infarct volume (FIV) in acute ischaemic stroke (AIS) without reperfusion. T_max thresholds are derived from Western ethnic populations but not from ethnic Asian populations. We aimed to investigate the influence of ethnicity on T_max thresholds. Methods: From a clinical-imaging registry of Australian and Indonesian stroke patients, we selected a participant subgroup with the following inclusion criteria: AIS under 24 h and absence of reperfusion therapy. Clinical data included demographics, time metrics, stroke severity, pre-morbid, and 3-month Modified Rankin Score. Baseline computed tomography perfusion and MRI <72 h were performed. Volumes of T_max utilizing different thresholds and FIVs were calculated. Spearman correlation was used to evaluate relationship involving ordinal variables and calculate the optimal T_max threshold against FIV in both populations. Results: Two hundred patients were included in the study sample, 100 in Jakarta and 100 in Geelong. The median National Institutes of Health Stroke Scale (IQR) were 6 (3-11) and 3 (1-5), respectively. Themedian T_max+6 (IQR) was 0 (0-46.5) in Jakarta group and 0 (0-7.5) in Geelong group. The median FIV (IQR) was 0 (0-30.5) and 0 (0-5.5). T_max+8 s in Jakarta population against FIV showed Spearman's coefficient ρ = 0.72, representing the optimal T_max threshold. T_max+6 s showed Spearman's coefficient ρ = 0.51 against FIV in the Geelong population. Conclusion: T_max thresholds approximating FIV were possibly different in the Asian when compared with the non-Asian populations. Future studies are required to extend and confirm the validity of our findings.