When Evidence Goes "Missing in Action": Implications for Patient Management in Cardiac Surgery

Best-practice clinical decision-making for patient blood management (PBM) and transfusion in cardiac surgery requires high-quality, timely information. However, evidence will be misleading if published information lags too far behind evolving practice, or if trial results are biased, incomplete, or unreported. The result is that providers are deprived of accurate data, and patients will not receive best possible care. Publicly accessible trial registries provide information for structured audits of reporting compliance, and appraisal of evidence attrition and distortion. Trials related to blood management and transfusion in cardiac surgery and those registered in ClinicalTrials.gov were evaluated for relevance, reliability, transparency, timeliness, and prevalence of unreported trial results. Evidence was considered to have "disappeared" if no results were posted to the registry and no related PUBMED publications were available by July 2019. Data were summarized by descriptive statistics. A total of 181 registered trials were surveyed; 52% were prospectively registered. Most commonly reported primary outcomes were laboratory surrogate measures (34%). Patient- and practice-relevant outcomes-mortality/major morbidity (7%), transfusion (27%), and major bleeding (28%)-were less common. Only seven studies posted results to the registry within the mandated 12 months from study completion; median time to posting was 17 (interquartile range [IQR] 13, 37) months. Trial results for 58% were unreported 3-9 years after trial completion. A staggering amount of clinical trial evidence for PBM in cardiac surgery is missing from publicly accessible records and the literature. Investigators must be incentivized to promptly and completely report all results. Penalties for noncompliance are already in place and should be enforced. Simplified information linkage, centralized and routine audit cycles, and prioritization of robust "living" reviews may be more positive motivators. Implementation will require a sea change in the prevailing culture of research reporting, plus coordinated efforts of clinicians, applied statisticians, information technology specialists, and research librarians.