Crit Care Med 2021 Feb 15. Epub 2021 Feb 15.
Department of Critical Care Medicine, The Clinical Research, Investigation, and Systems Modeling of Acute illness (CRISMA) Center, University of Pittsburgh School of Medicine, Pittsburgh, PA. Anaesthesia, Critical Care, and Pain Medicine, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom. Division of Pulmonary and Critical Care Medicine, University of California San Francisco, San Francisco, CA. Division of Pediatric Critical Care Medicine, Department of Critical Care Medicine, Children's Hospital of Pittsburgh, Pittsburgh, PA. Department of Medicine, University of Pittsburgh, Pittsburgh, PA. Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA. Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Michigan, Ann Arbor, MI. Division of Anaesthetics, Pain Medicine, and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom. Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom. Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN. Kaiser Permanente Division of Research, Oakland, CA. Keenan Research Centre for Biomedical Science, St Michael's Hospital, Toronto, ON, Canada. Department of Anesthesiology, Critical Care and Pain Medicine, Boston Children's Hospital, Boston, MA. Center for Experimental and Molecular Medicine, Amsterdam University Medical Centers, Location Academic Medical Center, University of Amsterdam, Amsterdam, NL. Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Amsterdam University Medical Centers, location Academic Medical Center, University of Amsterdam, Amsterdam, NL. Guy's and St Thomas' NHS Foundation Trust, ICU support Offices, St Thomas' Hospital, London, United Kingdom. School of Immunology and Microbial Sciences, Kings College London, London, United Kingdom. Department of Emergency Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA. Inflammatix, Burlingame, CA. Department of Intensive Care Medicine, Nepean Hospital, Sydney, AU. Division of Pulmonary and Critical Care Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA. Department of Medicine, Center for Applied Genomics and Precision Medicine, Duke University School of Medicine, Durham, NC. Division of Critical Care Medicine, Cincinnati Children's Hospital Medical Center and Cincinnati Children's Research Foundation, Cincinnati, OH. Department of Critical Care Medicine, Peking University People's Hospital, Beijing, China.
Sepsis is defined as a dysregulated host response to infection that leads to life-threatening acute organ dysfunction. It afflicts approximately 50 million people worldwide annually and is often deadly, even when evidence-based guidelines are applied promptly. Many randomized trials tested therapies for sepsis over the past 2 decades, but most have not proven beneficial. This may be because sepsis is a heterogeneous syndrome, characterized by a vast set of clinical and biologic features. Combinations of these features, however, may identify previously unrecognized groups, or "subclasses" with different risks of outcome and response to a given treatment. As efforts to identify sepsis subclasses become more common, many unanswered questions and challenges arise. These include: 1) the semantic underpinning of sepsis subclasses, 2) the conceptual goal of subclasses, 3) considerations about study design, data sources, and statistical methods, 4) the role of emerging data types, and 5) how to determine whether subclasses represent "truth." We discuss these challenges and present a framework for the broader study of sepsis subclasses. This framework is intended to aid in the understanding and interpretation of sepsis subclasses, provide a mechanism for explaining subclasses generated by different methodologic approaches, and guide clinicians in how to consider subclasses in bedside care.