Chapter 16 Laboratory Assessment

TABLE 16.1 Laboratory Screening for Hydration Status Laboratory Test Osmolality

Normal Values Adults: 285–295 mOsm/kg H2 Serum sodium Albumin Urea nitrogen BUN:creatinine ratio

136-145 mEq/L 136-145 mmol/L

3.5–5 g/dL 35–50 g/L

10-20 mg/dL 3.6–7.1 mmol/L

10:1 Abbreviation: BUN, blood urea nitrogen.

Source: Adapted with permission from Litchford MD. Laboratory Assessment of Nutritional Status: Bridging Theory & Practice. Greensboro, NC: CASE Software; 2011.

215

Dehydration

O > 295 mOsm/kg H2 > 145 mEq/L

O

Overhydration

< 285 mOsm/kg H2 < 130 mEq/L

Higher than normal Elevated > 25:1 Lower than normal Lower than normal < 10:1 O

transfusion reflect the nutritional status of the blood donor, not the person who received the transfusion. This is a short-term solution that increases the iron levels while the body begins to use nutrients from food. The initial assessment must consider the impact of blood products, the withdrawal of fluids, and other medical procedures that may change the short- and long-term nutritional status of the older adult (3).

REFERENCE STANDARDS “Standard laboratory reports are referenced using sug- gested 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 the very old is limited. Reference standards may not apply to these age groups.” This is an important concern in assessing older adults because the norms of older adults appear to be slightly lower or higher than standard norms. However, acceptable differences have yet to be defined. Registered dietitian nutritionists (RDNs) must consider how the standards were developed (1). Assessment of nutritional status must be viewed in the unique context of each client. “The frequency of tests; the technology used; and the age, disease state, and stress level of the patient/resident must be consid- ered. Laboratory tests are an essential tool for improv- ing health outcomes and reducing costs” (1).

EQUIPMENT

Changes in nutritional status are measured most accu- rately by using laboratory test results from the same laboratory. “Comparing laboratory results from differ- ent institutions can be like comparing apples to oranges. Each institution establishes reference stan- dards and laboratory procedures for each test, as sug- gested by the equipment manufacturer.” Variation can also include “equipment used, the degree of equipment calibration, and the skill of the technician” (1).

CONSIDERATIONS FOR REQUESTING LABORATORY TESTS

As a member of the health care team, the RDN should consider the following questions when requesting addi- tional laboratory tests:

1. Will the outcome actually change the nutrition care plan?

Example: The care of a client with AIDS is being directed by a hospice nurse. The client is not eating and is losing weight. The protein status is likely declining. The client is receiving comfort measures only. Requesting a prealbumin test will not change the nutrition care plan. Knowing the degree to which the protein status is declining will not change the plan of care. In other words, the client would most likely not receive addi- tional oral nutritional supplements or enteral or parenteral support as a means to improve nutri- tional status (1).