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Overview

Nutrition Care Process (NCP) is a systemic problem-solving method for RDs to use to think critically and make decisions to address nutrition problems. The goal is provide high quality care documented using standardized language.

All steps of NCP can incorporate laboratory values. In the Nutrition Assessment step, practitioners are to review data, cluster nutrition care indicators and identify standards by which the data will be compared. Next, determine the Nutrition Diagnosis. Under the clinical domain, biochemical section, are the nutrition diagnosis specifically related to changes in laboratory values. Laboratory values may be incorporated into PES statements in the signs and symptoms section as well. In the final step of NCP, Nutrition Monitoring and Evaluation, laboratory data may be useful to determine if Nutrition Diagnoses are resolved or new ones are present. It is important to remember that requesting more laboratory testing does not always equate with best practices. Centers for Medicare (CMS) F-tag 314, Comprehensive Assessment under nutrition, malnutrition & hydration deficits states:

‘Although some laboratory tests may help clinicians evaluate nutritional issues in a resident with pressure ulcers, no laboratory test is specific or sensitive enough to warrant serial/repeated testing.

Serum albumin, prealbumin and cholesterol may be useful to help establish overall prognosis; however, they may not correlate well with clinical observation of nutritional status.’

Incorporating laboratory assessment as a tool to assess nutrition status is supported in the research literature and used by other medical team members. Laboratory Assessment of Nutritional Status: Bridging Theory & Practice is a reference to assist the healthcare practitioner in documenting the role of medical nutrition therapy through NCP.

Implications of Selected Laboratory Tests

Test selections are based on subjective clinical judgement, national recommendations and evidenced-based medicine. Patient’s knowledge of diagnostic screening tests may be from friends, family and the Internet. It is critical that patients understand that not all information on the Internet is reliable or pertinent to their unique medical status.

Not all tests are appropriate for all patients, i.e. creatinine excretion cannot be used to evaluate muscle mass in patients with renal failure because the test assumes normal renal function. Remember that the overall medical condition of the patient, the current medications, and the psychoneuroimmunology must be considered in the interpretation of laboratory tests.

Changes in Nutritional Status

A single laboratory test may or may not reflect improved nutritional status once a medical nutrition therapy intervention program has begun. Changes in hydration status significantly affect the laboratory results. More than one laboratory test is required to accurately document changes in nutritional status. Using support data such as physical findings, changes in anthropometric data, reported symptoms and diet will increase confidence in laboratory results.

Impact of Inflammation

Interpreting laboratory tests must include the impact of inflammatory stress. There are two types of inflammation, acute or innate and chronic. Acute inflammation is a short-term process in which inflammatory mediators have short half lives and are quickly degraded. This occurs following injury, surgery or trauma. Chronic, inappropriate inflammation occurs when the immune response to injury is not extinguished. The persistent immune response acts like a slow burning fire that stimulates the synthesis of proinflammatory cytokines which promote erosion of lean body mass. Chronic inflammation is one of the hallmarks and underlying contributor to many diseases.

Inflammatory response occurs with or without infection. The classic signs are redness, swelling, pain, heat and loss of function. When the inflammation occurs in internal organs or structures, all the classic signs of inflammation may not be present. Inflammation triggers an immune response which initiates the release of both proinflammatory and anti-inflammatory cytokines. To combat the proinflammatory cytokines, the body must mobilize nutrient stores to produce acute phase proteins and T and B lymphocytes.

Acute Phase Proteins

Acute phase proteins are either positive or negative. In the presence of inflammation, with or without infection, the synthesis of positive acute phase proteins increases dramatically at the expense of the negative acute phase proteins. The concentration of positive acute phase proteins increases by at least 25 percent following an inflammatory response. Values can increase to 1000 times normal. Some of the inflammatory markers are specific while others are non-specific to the source of inflammation. Tracking the positive acute phase proteins to determine when inflammatory process wanes may be misleading if inflammation improves in one area while other underlying areas of inflammation may be present. Table 1 categorizes selected acute phase proteins as either positive or negative.

Negative acute phase proteins plummet in the presence of inflammation. Levels decrease by at least 25 percent. For example, a 25 percent drop in an albumin of 3.0 g/dL would be 2.25 g/dL. The albumin does not evaporate or disintegrate. It simply shifts from the extravascular space to the plasma.

Table 1. Selected Acute Phase Proteins

Positive Acute Phase Proteins	Negative Acute Phase Proteins
•C-reactive protein (CRP)	•Albumin
•hs-CRP	•Prealbumin
•Fibrinogen	•Transferrin
•Plasminogen-activator-inhibitor 1 (PAI-1)	•Insulin-like growth factor 1
•Serum amyloid A
•Ferritin
•Ceruloplasmin

Reference Standards

Standard laboratory reports are referenced using suggested normal or age-appropriate values. Remember that many reference standards were developed based upon clinical research using primarily young and middle aged adults. Clinical research on the very young and very old is limited. Reference standards may not apply to these age groups. This is of particular concern in assessing the growing elderly population because their norms appear to be slightly lower or higher than the standards, but the acceptable difference has yet to be defined. Some manufacturers of laboratory assay equipment have developed age reference standards using their databases. The director of your institution's laboratory will be able to assist you in evaluating the available database and in incorporating the equipment specific reference standards into the laboratory reports generated for each individual.

Equipment

The most accurate measure of changes in nutritional status is using laboratory results from the same institution. Comparing laboratory results from different institutions can be like comparing apples to oranges. Each institution establishes reference standards and laboratory procedures for each test as suggested by the manufacturer. Other sources of variation include equipment used, the degree of equipment calibration and the skill of the technician.