The ABCDs of nutritional assessment in infectious diseases research.

Malnutrition is the most common acquired cause of immunodeficiency worldwide. Nutritional deficiencies can blunt both the innate and adaptive immune response to pathogens. Furthermore, malnutrition is both a cause and consequence of infectious diseases. The bidirectional relationship between infectious diseases and undernutrition, as well as the inflammatory milieu of infectious diseases, can complicate nutritional assessment. This article aims to provide clinicians and researchers with an overview of commonly used tools to assess nutritional status, with a particular emphasis on their use in the context of infectious diseases. This includes anthropometric, biochemical, clinical/physical, and dietary assessments to screen and evaluate undernutrition, diet quality, and food insecurity effectively.