Nutrition screening, assessment, and intervention in patients with malnutrition are key components of nutrition care (Figure 1). Nutrition screening has been defined by the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.) as "a process to identify an individual who is malnourished or who is at risk for malnutrition to determine if a detailed nutrition assessment is indicated."1 In the United States, the Joint Commission mandates nutrition screening within 24 hours of admission to an acute care center.2 The goal of nutrition assessment is to identify any specific nutrition risk(s) or clear existence of malnutrition. Nutrition assessments may lead to recommendations for improving nutrition status (eg, some intervention such as change in diet, enteral or parenteral nutrition, or further medical assessment) or a recommendation for rescreening.3-5 Nutrition assessment has been defined by A.S.P.E.N. as "a comprehensive approach to diagnosing nutrition problems that uses a combination of the following: medical, nutrition, and medication histories; physical examination; anthropometric measurements; and laboratory data."1 A nutrition assessment provides the basis for a nutrition intervention. Indeed, these definitions are consistent with the Joint Commission's interpretation of a screen as an instrument used to determine whether additional information (from an assessment) is required to warrant an intervention.2 Nutrition assessment performed by a nutrition support clinician is a rigorous process that includes obtaining diet and medical history, current clinical status, anthropometric data, laboratory data, physical assessment information, and often functional and economic information; estimating nutrient requirements; and, usually, selecting a treatment plan. Clinical skill, resource availability, and the setting determine the specific methods used to perform a clinical nutrition assessment.6,7 Evidence-based Clinical Guidelines for specific diseases and conditions may identify assessment parameters appropriate to those conditions. In addition, reassessment and monitoring methods are an extension of the assessment process within overall nutrition care (Figure 1). As illustrated in Figure 1, clinical assessment (including rescreening and reassessment) is a continuous process. Nutrition care algorithm.3 Experts define malnutrition as "an acute, subacute or chronic state of nutrition, in which varying degrees of overnutrition or undernutrition with or without inflammatory activity have led to a change in body composition and diminished function."1 Parameters used to diagnose malnutrition in the screening and assessment processes reflect both nutrition intake and severity and duration of disease. These factors may lead to changes in body habitus and metabolic alterations associated with poor outcome. An International Consensus Guideline Committee has proposed an approach to diagnosing malnutrition in adults based on etiology, thus integrating the present understanding of inflammatory responses to disease and trauma.8,9 The committee proposed the following nutrition diagnoses: (1) starvation-related malnutrition, which is chronic starvation without inflammation, (2) chronic disease–related malnutrition, where inflammation is chronic and of mild to moderate degree, and (3) acute disease or injury–related malnutrition, where inflammation is acute and severe. Inflammation and related compensatory mechanisms associated with disease or injury may cause anorexia and alterations in body composition and stress metabolism. Metabolic alterations associated with inflammation are predominantly cytokine mediated and persist as long as the inflammatory stimulus is present. These metabolic alterations include elevated energy expenditure, lean tissue catabolism (proteolysis), fluid shift to the extracellular compartment, acute phase protein changes, and hyperglycemia. Decreased synthesis of negative acute phase proteins will result in reduced serum albumin, transferrin, prealbumin, and retinol binding protein concentrations that are potent indicators of poor outcome. Indeed, experts have advised that albumin and prealbumin not be used in isolation to assess nutrition status because they are fundamentally markers of inflammatory metabolism.9-11 Positive acute phase proteins such as C-reactive protein are also potent predictors of morbidity and mortality and are elevated in the presence of inflammation.10 Table 1 lists screening and assessment instruments commonly cited in the literature12 and used in the articles evaluated for these Clinical Guidelines. The table segregates parameters used in these instruments that are primarily related to anthropometry and diet, primarily related to severity of illness (disease and trauma), or other (including physical and psychological variables). Malnourished states are associated with metabolic alterations caused by disease- and trauma-triggered inflammatory response.9 These instruments were generally developed to predict or assess undernutrition. Overnutrition and obesity are generally assessed using the body mass index and/or waist circumference guidelines in Table 2. These Clinical Guidelines will compare clinical outcomes associated with published nutrition screening and assessment tools and the impact of further clinical assessment and nutrition intervention on clinical outcomes. A.S.P.E.N. consists of healthcare professionals representing the disciplines of medicine, nursing, pharmacy, dietetics, and nutrition science. The mission of A.S.P.E.N. is to improve patient care by advancing the science and practice of nutrition support therapy. A.S.P.E.N. vigorously works to support quality patient care, education, and research in the fields of nutrition and metabolic support in all healthcare settings. These Clinical Guidelines were developed under the guidance of the A.S.P.E.N. Board of Directors. Promotion of safe and effective patient care by nutrition support practitioners is a critical role of A.S.P.E.N. The A.S.P.E.N. Board of Directors has published Clinical Guidelines since 1986.26-28 A.S.P.E.N. evaluates in an ongoing process when individual Clinical Guidelines should be updated. These A.S.P.E.N. Clinical Guidelines are based upon general conclusions of health professionals who, in developing such guidelines, have balanced potential benefits to be derived from a particular mode of medical therapy against certain risks inherent with such therapy. However, the professional judgment of the attending health professional is the primary component of quality medical care. Because guidelines cannot account for every variation in circumstances, the practitioner must always exercise professional judgment in their application. These Clinical Guidelines are intended to supplement, but not replace, professional training and judgment. These Clinical Guidelines were created in accordance with Institute of Medicine recommendations as "systematically developed statements to assist practitioner and patient decisions about appropriate healthcare for specific clinical circumstances."29 These Clinical Guidelines are for use by healthcare professionals who provide nutrition support services and offer clinical advice for managing adult and pediatric (including adolescent) patients in inpatient and outpatient (ambulatory, home, and specialized care) settings. The utility of the Clinical Guidelines is attested to by the frequent citation of these documents in peer-reviewed publications and their frequent use by A.S.P.E.N. members and other healthcare professionals in clinical practice, academia, research, and industry. They guide professional clinical activities, they are helpful as educational tools, and they influence institutional practices and resource allocation.30 These Clinical Guidelines are formatted to promote the ability of the end user of the document to understand the strength of the literature used to grade each recommendation. Each guideline recommendation is presented as a clinically applicable statement of care and should help the reader make the best patient care decision. The best available literature was obtained and carefully reviewed. Chapter author(s) completed a thorough literature review of publications from 2005 to 2009 using Medline®, the Cochrane Central Registry of Controlled Trials, the Cochrane Database of Systematic Reviews, and other appropriate reference sources. These results of the literature search and review formed the basis of an evidence-based approach to the Clinical Guidelines. Chapter editors worked with the authors to ensure compliance with the authors' directives regarding content and format. Then the initial draft was reviewed internally to promote consistency with the other A.S.P.E.N. Clinical Guidelines and Standards and externally reviewed (by experts in the field either within our organization or outside of our organization) for appropriateness of content. The final draft was reviewed and approved by the A.S.P.E.N. Board of Directors. The system used to categorize the level of evidence for each study or article used in the rationale of the guideline statement and to grade the guideline recommendation is outlined in Table 3.31 The grade of a guideline is based on the levels of evidence of the studies used to support the guideline. A randomized controlled trial (RCT), especially one that is double blind in design, is considered to be the strongest level of evidence to support decisions regarding a therapeutic intervention in clinical medicine.31 A systematic review (SR) is a specialized type of literature review that analyzes the results of several RCTs. A high-quality SR usually begins with a clinical question and a protocol that addresses the method to answer this question. These methods usually state how the literature is identified and assessed for quality, what data are extracted and how they are analyzed, and whether there were any deviations from the protocol during the course of the study. In most instances, meta-analysis (MA), a mathematical tool to combine data from several sources, is used to analyze the data. However, not all SRs use MAs. SRs and MAs are used in these Clinical Guidelines only to organize the evidence but are not used in the grading process. A level of I, the highest level, was given to large RCTs where results were clear and the risk of α and β error is low (well-powered). A level of II was given to RCTs that include a relatively small number of patients or are at moderate to high risk for α and β error (underpowered). A level of III was given to cohort studies with contemporaneous controls or validation studies, and cohort studies with historic controls received a level of IV. Case series, uncontrolled studies, and articles based on expert opinion alone received a level of V. Table 4 provides the entire set of guideline recommendations for Adult Nutrition Screening and Assessment. 1. Screening for nutrition risk is suggested for hospitalized patients: Grade E Nutrition risk, identified by nutrition screening, is associated with longer length of hospital stay, complications, and mortality. Nutrition screening is the first step in nutrition care. In varied adult populations, patients who are identified as malnourished by various screening tools have longer length of hospital stay,33,34,36,37 and complications.23,35-40 Mortality risk is also predicted by malnutrition screening (Table 5).36,39,41 2. Nutrition assessment is suggested for all patients who are identified to be at nutrition risk by nutrition screening: Grade E Malnourished patients, identified by nutrition assessment tools, have more complications and longer hospitalizations than do patients with optimal nutrition status. Such patients, identified by nutrition assessment tools, have more infectious and noninfectious complications,16,39 longer hospital length of stay,33,42,44 and greater mortality.42,46,47 With one exception,46 studies have shown malnourished patients to have greater mortality (Table 6). 3. Nutrition support intervention is recommended for patients identified by screening and assessment as at risk for malnutrition or malnourished: Grade C Nutrition support intervention in patients identified by screening and assessment as at risk for malnutrition or malnourished may improve clinical outcomes. This guideline places nutrition assessment and screening in the context of intervention as part of nutrition care.23,48-51 Nutrition intervention in malnourished patients was associated with improved nutrition status,48,49 nutrient intake,50 physical function,49,51 and quality of life.51 In addition, hospital readmissions were reduced (Table 7).48,51 A.S.P.E.N. Board of Directors providing final approval: Charles Van Way III, MD (Chair); Mark DeLegge, MD; Carol Ireton-Jones, PhD, RD, LD, CNSD; Tom Jaksic, MD, PhD; Elizabeth M. Lyman, RN, MSN; Ainsley M. Malone, RD, MS; Stephen A. McClave, MD; Jay M. Mirtallo, MS, RPh, BCNSP, FASHP; Lawrence A. Robinson, PharmD; W. Frederick Schwenk MD, CNSP; and Daniel Teitelbaum, MD.