Embracing Heterogeneity in The Multicenter Stroke Preclinical Assessment Network (SPAN) Trial
Authors: Morais Andreia , Locascio Joseph J. , Sansing Lauren H. , Lamb Jessica , Nagarkatti Karisma , Imai Takahiko , van Leyen Klaus , Aronowski Jaroslaw , Koenig James I. , Bosetti Francesca , Lyden Patrick , Ayata Cenk , Bosetti Francesca , Koenig James I. , Lyden Patrick D. , Lamb Jessica , Nagarkatti Karisma , Hess David C. , Kamat Pradip K. , Khan Mohammad Badruzzaman , Dhandapani Krishnan , Arbab Ali S. , Siddiqui Shahneela , Smith Cameron , Nisar Mohammad , Leira Enrique C. , Chauhan Anil K. , Dhanesha Nirav , Patel Rakesh B. , Kumskova Mariia , Thedens Daniel , Wang Kai , Ayata Cenk , Morais Andreia , Imai Takahiko , Qin Tao , Jin Xuyan , Erdogan Taylan Denis , Yu Lili , Mandeville Joseph B. , Kimberly William Taylor , Whittier Jonah Patrick Weigand , Lo Eng , Arai Ken , Van Leyen Klaus , Sansing Lauren H. , Hyder Fahmeed , Mihailovic Jelena M. , Sanganahalli Basavaraju G. , Diaz-Perez Sebastian , Velazquez Sofia E. , Beatty Hannah E. , Johnson Conor , Herman Alison L. , Boisserand Ligia S. B. , Immakavar Emma , Koehler Raymond C. , Dawson Ted , Dawson Valina , Shi Yanrong , Avery Brooklyn , Lannon Steven , Bibic Adnan , Akhter Kazi , Karuppagounder Senthilkumar S. , Aronowski Jaroslaw , McCullough Louise D. , Obertas Lidiya , Goh Andrew , Huang Shuning , Chauhan Anjali 
Published: January 2023

The Stroke Preclinical Assessment Network (SPAN) is a multicenter preclinical trial platform using rodent models of transient focal cerebral ischemia to address translational failure in experimental stroke. In addition to centralized randomization and blinding and large samples, SPAN aimed to introduce heterogeneity to simulate the heterogeneity embodied in clinical trials for robust conclusions. Here, we report the heterogeneity introduced by allowing the 6 SPAN laboratories to vary most of the biological and experimental model variables and the impact of this heterogeneity on middle cerebral artery occlusion (MCAo) performance. We included the modified intention-to-treat population of the control mouse cohort of the first SPAN trial (n=421) and examined the biological and procedural independent variables and their covariance. We then determined their impact on the dependent variables cerebral blood flow drop during MCAo, time to achieve MCAo, and total anesthesia duration using multivariable analyses. We found heterogeneity in biological and procedural independent variables introduced mainly by the site. Consequently, all dependent variables also showed heterogeneity among the sites. Multivariable analyses with the site as a random effect variable revealed filament choice as an independent predictor of cerebral blood flow drop after MCAo. Comorbidity, sex, use of laser Doppler flow to monitor cerebral blood flow, days after trial onset, and maintaining anesthesia throughout the MCAo emerged as independent predictors of time to MCAo. Total anesthesia duration was predicted by most independent variables. We present with high granularity the heterogeneity introduced by the biological and model selections by the testing sites in the first trial of cerebroprotection in rodent transient filament MCAo by SPAN. Rather than trying to homogenize all variables across all sites, we embraced the heterogeneity to better approximate clinical trials. Awareness of the heterogeneity, its sources, and how it impacts the study performance may further improve the study design and statistical modeling for future multicenter preclinical trials.