Nutrition 411: Changing the Malnutrition Paradigm
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The Merriam Webster Dictionary defines malnutrition as “faulty nutrition due to inadequate or unbalanced intake of nutrients or their impaired assimilation or utilization”.1 This classic dictionary definition may work for grade school and middle school science classes but is no longer applicable for diagnosing adult patients. In recent years, it has become clear that malnutrition is a complex syndrome that manifests in different ways. As a result of this new understanding, the definition of the condition and how to diagnose it have been subject to intense scientific scrutiny. Many clinicians struggle to understand this change and wonder what parameters to use in order to assign a diagnosis of malnutrition. In an attempt to understand the whys and wherefores of recent changes in the malnutrition paradigm, a summary of the evidence follows.
Historically, a diagnosis of protein energy malnutrition (PEM) was made using serum albumin and/or prealbumin. Malnutrition was classified as mild, moderate, or severe based on a patient’s serum hepatic protein levels. Table 1 outlines the malnutrition parameters that were standard in medical, nursing, and nutrition textbooks for generations. Many patients were labeled with a diagnosis of “severe malnutrition” when their serum albumin level was below 2.0, and the appropriate ICD-9 code was applied. Persons with low serum albumin or prealbumin often were referred to a registered dietitian (RD) and/or prescribed a protein supplement in an effort to correct their malnutrition. Serial serum albumin and prealbumin levels were requested to track nutritional status in patients with pressure ulcers, surgical wounds, and a host of other medical conditions.
Fast-forward to 2013, when evidence shows that although serum albumin and prealbumin may be good indicators of morbidity and mortality, they are not accurate indicators of malnutrition.2-5 The relevance of the entire class of hepatoprotein laboratory tests, including serum albumin, as indicators of malnutrition is now believed to be limited.3 This information has been documented in the literature for nearly 10 years but has admittedly been slow to trickle down to practicing physicians, nurses, and dietitians. Despite the volume of evidence to the contrary, it is still common to see a diagnosis of malnutrition based on a low albumin or prealbumin in medical records. Many clinicians still are confused by the subject and rely on albumin and prealbumin in the absence of other clear indicators of malnutrition. An understanding of the science behind the expert opinions can help practitioners understand why serum proteins are not effective for a malnutrition diagnosis.
Understanding Protein Lab Data
Albumin and prealbumin are negative acute-phase reactants — ie, they decrease in the presence of inflammation in the body.2,4 Inflammation can be defined as “the aggregate of clinical, hematologic, and organ function abnormalities associated with sepsis, trauma, and a variety of other conditions such as pancreatitis”.2 The inflammatory response is a complex series of cellular reactions that results in catabolism and breakdown of lean body mass. Inflammatory conditions that affect serum albumin levels include (but aren’t limited to) dehydration, hepatic failure, infection, cancer, bed rest, and pregnancy.2,4 In reality, almost every chronic medical condition and most acute conditions can potentially result in a decrease in serum prealbumin and/or albumin because of the inflammatory response.