Implications for Practice
Laboratory Assessment of Nutritional Status: Bridging Theory & Practice was designed to be used by RDs, RNs, case managers, DTRs, CDMs and healthcare science students as a reference tool. It includes over 90 laboratory tests with a nutritional significance. Laboratory tests include normal values, critical values, nutritional significance, disease states that increase or decrease results and medications which may increase or decrease results. All laboratory values are listed in alphabetical order for easy reference. An index is provided for cross reference.
Biochemical Assessment of Nutritional Status
Biochemical assessment is an essential tool to assess the body’s ability to convert food into body components. It is the foundation of the nutrition intervention program, one of the measuring sticks by which to evaluate its success and to predict medical outcomes.
National trends indicate a declining number of laboratory tests are being ordered in all areas of health care. This trend is a reflection of a better understanding of the predictive value of certain tests and cost-reduction programs nationwide. Assessment of physical and nutritional status is done primarily through physical assessment and observed dietary intake. Justification for ordering laboratory tests is based on observed clinical signs and symptoms.
Laboratory tests are based on analysis of blood and urine samples, which contain nutrients, enzymes and metabolites that reflect protein, vitamin and mineral status, presence of other components in body fluids. Common studies include enzymes, serum lipids, electrolyte levels, red and white blood cell counts, clotting factors and breakdown products such as urea nitrogen.
Blood
The pH of the blood is in a range between 7.36 and 7.44. The buffer system helps to maintain the pH within this narrow range.
An increase or decrease in the cellular elements or constituents of the blood can be indicative of a nutritional deficiency, disease and acute or chronic blood loss. Blood analysis results are used for diagnosis as well as following the course of the deficiency, disease or recovery from injury or trauma.
Urine
Urine is a mixture of water, inorganic salts and organic compounds. The major inorganic ions excreted are cations, sodium, potassium, calcium, magnesium and ammonium. The anions are chloride, phosphate and sulfate. The nitrogenous and non-nitrogenous organic compounds excreted in the urine are the waste products of metabolism. Water-soluble vitamins and their metabolites may be excreted in the urine. The volume of urine excreted is approximately 600 to 2500 mL per day. The normal pH range of urine is between 4.6 and 8.0 with an average of 6.0 (Pagana, 2009), depending on time of sampling and what food was consumed. The specific gravity of urine falls between 1.005 and 1.029 (Pagana, 2009), but can be affected by dehydration, renal disease, diabetes, fever and aging.
Urinalysis reports include remarks about the color, appearance and odor of the urine. Tests performed include pH, presence of protein, glucose, ketones, blood, and leukocyte esterase. The urine is examined microscopically for red and white blood cells (WBC), casts, crystals and bacteria. While nutritional assessment has focused primarily on blood analysis, some urine tests are included.
Assessment of Hydration Status
Dehydration is the most common fluid electrolyte disorder of frail older adults living in community or institutional settings (Lavizzo-Mourey, 1988). Since no single measure has proved to be the ‘gold standard’ in the diagnosis of dehydration, it is often overlooked or misdiagnosed (Faes, 2007). Dehydration is a special concern for the hospitalized patient and long-term care resident. It is one of the most frequent diagnoses for admission to the hospital for patients 65 years and older. Mortality of patients with dehydration is high if not treated adequately and in some studies exceeds 50 percent (Bourdel-Marchesson, 2004). In terms of morbidity, several studies have shown an association between severe dehydration and poor mental function (Seymour, 1980; Wilson, 2003). Other studies found that dehydration was a significant risk factor for developing thromboembolic complications, infectious disease, kidney stones and obstipation (fecal impaction) (Embon, 1990; Wrenn, 1989).
Total body water accounts for about 60 percent of total body weight of middle-aged adults and about 45 – 50 percent of total body weight of elderly adults (Narins, 1994). The clinical significance of these numbers is that the elderly reach clinical dehydration faster than younger adults. Total body fluids decline in the elderly primarily because of a change in body composition. With age, older adults tend to lose lean muscle mass and gain fat. Lean muscle mass contains a higher percentage of water than fat which contains very little water. Changes in fluid balance in seniors can have a dramatic impact on their health and well-being (Chidester, 1997; Inouye, 1999; Rauscher, 2001; Welch, 1998).
Persons who are seriously ill and older adults tend to have a decreased thirst sensation due to confusion, an altered state of consciousness, or severe depression. Dehydration can occur during episodes of illness, fever, diaphoresis and inadequate replacement fluids. Fluid needs increase by 7 percent per degree of fever measured in Fahrenheit and
