Older Adult Labs Medsurg

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MEDSURG NURSINGCE Objectives and Evaluation Form appear on page 230.

Interpreting Laboratory Values In Older AdultsNancy Edwards Carol Baird Results of common laboratory tests must be interpreted with care in older adults. Laboratory results that vary with age are presented, along with possible causes and interpretations of results.

J

Nancy Edwards, PhD, RN,C, is an Associate Professor, Purdue University School of Nursing, West Lafayette, IN. Carol Baird, DNS, APRN, BC, is an Associate Professor, Purdue University School of Nursing, West Lafayette, IN.

ohn Doe, 83 years old, comes to the clinic complaining of increasing fatigue and weakness. His past medical history includes diabetes mellitus, chronic anemia, and hypertension. The 510 man is thin (148 pounds) with small muscle mass. His skin color is pale pink. A battery of diagnostic tests reveals the following: hemoglobin 11.2 g/dL, hematocrit 40%, white blood cells 5,000/ml, fasting blood sugar 183 mg/dL, blood urea nitrogen 30 mg/dL, serum creatinine 1.9 mg/dL, and serum albumin 2.3 g/dL. The nurse is uncertain which laboratory values are significant in considering Mr. Does care plan. This case illustrates the difficulty in interpreting laboratory values for older adults, which is a complex task with varied opinions about what is normal. Multiple confounding factors make interpretation and use of laboratory results in older patients challenging. Some of the factors include (a) physiologic changes associated with aging, (b) the high prevalence of chronic conditions, (c) changes in nutrition and fluid consumption, (d) lifestyle changes, and (e) pharmacologic regimes (Brigden & Heathcote, 2000). Laboratory test results also may be affected by many factors other than aging. Influencing factors

may include gender, body mass, alcohol intake, diet, and stress (Fischbach, 2004). Technical factors such as collection site, collection time, tourniquet application, and specimen transportation also can affect results but usually can be controlled by following standardized laboratory procedures (Brigden & Heathcote, 2000). Results of diagnostic testing in older adults may have different meanings from the results found in younger individuals. Nurses should recognize that no general trend exists for the direction of change in laboratory values for older adults. For some tests, older adults have higher than normal values and for others, lower values; some remain unchanged. Changes in laboratory values can be classified in three general groups: (a) those that change with aging; (b) those that do not change with aging; and (c) those for which it is unclear whether aging, disease, or both influence the values (Tripp, 2000). Common laboratory tests with interpretations for older adults are presented.

Interpreting Reference RangesThe accepted, normal ranges of values typically reported may not be applicable for older adults.

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Reference ranges may be more appropriate. Normal ranges are obtained by determining the mean of a random sample of healthy individuals, usually ages 20 to 40 years, in order to identify two standard deviations on either side of the mean. The concept of normal range, however, is not useful in determining age-related norms for older adults (Luggen, 2004). Reference ranges or reference values are preferred concepts. Reference ranges or reference values are those intervals within which 95% of the values fall for a specific population (Lab Tests Online, 2001). For example, geriatric reference ranges are those intervals within which 95% of values for persons over 70 years of age would fall. It must be cautioned, however, that some researchers recommend not using reference ranges for laboratory test parameters pertaining to older adults because it is difficult to differentiate whether results are a sign of a disease or are related to normal aging (Luggen, 2004). However, reference ranges are useful in some situations. The use of reference ranges allows for recognition of the special needs of the population in question. Reference ranges are calculated not just for older adults, but also for neonates (especially low-birthrate infants), adolescents, and pregnant women. In addition, specific reference ranges are known for tests for other special populations (for example, serum erythropoietin in adult athletes such as marathon runners). Laboratory values falling outside the normal ranges may indicate benign or pathologic conditions in the older adult (Fischbach, 2004). Values within the expected normal reference ranges, however, may also indicate new or progressing patho-

logic conditions in certain older adults. Nurses working with older adults should consider the total assessment rather than simply relying on laboratory diagnostic testing. For example, goals of management of diabetes should be individualized. The principal goal would be to enhance quality of life without undue risk of hypoglycemia. It usually is best to achieve fasting blood glucose levels of less than 140 mg/dl. However, in the frail elderly, it is best to avoid fasting or bedtime plasma glucose levels of less than 100 mg/dl if the patient is on insulin or sulfonylurea treatment (Reed & Mooradian, 1998). Serum creatinine is a second example of a laboratory test in which results may be within the specified reference range and yet indicate pathology for the older adult. Creatinine is a product of creatine phosphate, used in skeletal muscle contraction. Endogenous creatinine production is constant as long as muscle mass remains constant (Pagana & Pagana, 2002). The mechanisms that regulate the older individuals serum creatinine levels within the accepted reference range tend to overestimate renal functioning as a measure of glomerular filtration rate. Serum creatinine and blood urea nitrogen (BUN) levels in the high-normal category may represent significant renal dysfunction in the older adult who has inadequate protein intake (Daniels, 2002).

Specific Laboratory TestsHemoglobin (HGB). While the results of studies of the effects of aging on the hematologic system vary (Brigden & Heathcote, 2000; Nilsson-Ehle, Jagenburg, Landahl, & Swanborg, 2000), research does indicate that older individuals may have changes in hemoglobin and erythrocyte synthesis caused by changes in iron and vitamin B12

absorption (Giddens, 2004). Impaired erythrocyte production, blood loss, increased erythrocyte destruction, or a combination of conditions have also been identified as causes for lowered hemoglobin (Giddens, 2004). Kee (2002) defines hemoglobin as abnormal if less than 13.5 gm/dl for males and 12.0 gm/dl for females. Recent studies with older adults, however, suggest lower levels may be acceptable. The currently reported lowest acceptable value for older adults is 11.5 gm/dl for males and 11.0 gm/dl for females (Brigden & Heathcote, 2000) (see Table 1). Hemoglobin may be lower in older adults due either to normal aging changes or illnesses such as anemia. Manson and McCance (2004) identify impaired erythrocyte production, blood loss, increased erythrocyte destruction, or a combination of conditions as causes for anemia. Most instances of anemia are associated with chronic conditions such as renal insufficiency or gastric bleeding (Giddens, 2004). Anemia may be a serious condition because it places the older individual at greater risk for circulatory and oxygenation problems (Tripp, 2000). A reduction of hemoglobin can result in a decrease in oxygen content and an increase in fatigue. Signs of anemia may not be noticed if the anemia is mild, but some individuals may present with shortness of breath, fatigue, and paresthesia (Manson & McCance, 2004). A combination of vague symptoms and an unclear clinical picture may lead the health care provider to attribute the symptoms to old age and not to a treatable condition. Hematocrit (HCT). Changes in hematocrit may reflect fluid and/or nutritional status in the older adult (Fischbach, 2004; Giddens, 2004). An increase in the

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Table 1. Geriatric Laboratory Values and Interpretations of Hematology Normal Adult Value Male (M) Female (F) M 13.0 gm/dl F 12.0 gm/dl

Test Hemoglobin

Geriatric Value M 11.5 gm/dl F 11.0 gm/dl

Implications : Anemias, cirrhosis of liver, leukemias, Hodgkins disease, cancer (intestine, rectum, liver, or bone), kidney disease : Dehydration, COPD, CHF, polycythemia : Anemias, leukemia, Hodgkins disease, multiple myeloma, cirrhosis of liver, protein malnutrition, peptic ulcer, chronic renal failure, rheumatoid arthritis : Dehydration, severe diarrhea, polycythemia vera, diabetic acidosis, emphysema, transient cerebral ischemia : Hemotopoietic diseases, viral infections, alcoholism, systemic lupus erythematous (SLE), rheumatoid arthritis : Acute infection, tissue necrosis, leukemias, hemolytic anemia, parasitic diseases, stress : Idiopathic thrombocytopenia purpura, multiple myeloma, cancer, leukemias, anemias, liver disease, SLE, kidney disease : Polycythemia, trauma, post-splenectomy, metastatic carcinoma, pulmonary embolism, tuberculosis

Hematocrit

M 40% - 54% F 36% - 46%

M 30% - 45% F 36% - 65%

White Blood Cells

4,500 - 10,000 l/mm3

3,000 - 9,000 l/mm3

Platelets

150,000 - 400,000 l

Minimal change

Source: Brigden & Heathcote, 2000

hematocrit may signal volume depletion, while a decrease may be a result of conditions accompanied by fluid overload or dietary deficiencies. Hematocrit, the percentage of total blood volume that represents erythrocytes, may be normal if values are 30% to 45% for older males and 36% to 65% for older females (Desai & Isa-Pratt, 2002) (see Table 1). White blood cells (WBC). Whether total leukocyte count is affected by aging is controversial. However, there are definite changes in that the T cells are less responsive to infection (Fulop et al., 2001; Sester et al., 2002). Immunity gradually declines after age 30 to 40 years

(Rybka et al., 2003) (see Table 1). A decreased WBC value may result from specific disease (myeloma, collagen vascular disorders), infection or sepsis (pneumonia, urinary tract infections), or medications (cytotoxic agents, analgesics, phenothiazides), and should not be attributed to advancing age (Fischbach, 2004). This lowered WBC count in a healthy individual may result in an absence of elevated white blood cells in the presence of severe infection. Medications such as steroids also may influence the immune response (Giddens, 2004). Because of the slower immune response, common symptoms of infections, such as enlarged lymph glands,

fever, or pain, may be decreased in severity or absent in the older adult (Beers & Berkow, 2000). Nurses should be vigilant in efforts to detect other signs of infections in the older adult, such as confusion. Because of the concern for serious undetected infection, nurses should educate older adults about infection prevention techniques, such as hand washing and timely vaccination for influenza and pneumonia. Platelets (Plt). Aging usually causes a decline in bone marrow function, which may contribute to lowered platelet counts and decreased platelet function (Luggen, 2004). Studies also suggest that platelet adhesiveness increases with age, with no

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Table 2. Geriatric Laboratory Values and Interpretations of Erythrocyte Sedimentation Rate, Iron Metabolism, and Vitamin B12 Normal Adult Value Male (M) Female (F) M 0 - 15 mm/hr F 0 - 20 mm/hr

Test Erythrocyte Sedimentation Rate (ESR)

Geriatric Value M 0 - 40 mm/hr F 0 - 45 mm/hr

Implications : Polycythemia, CHF, degenerative arthritis, angina pectoris : Rheumatoid arthritis, rheumatic fever, acute MI, cancer (stomach, colon, breast, liver, kidney), Hodgkins disease, multiple myeloma, bacterial endocarditis, gout, hepatitis, cirrhosis of liver, glomerulonephritis, SLE, theophylline use. : Iron deficiency anemia, cancer (stomach, intestine, rectum, breast), bleeding peptic ulcers, protein malnutrition : Hemolytic, pernicious, and folic acid anemias; liver damage; lead toxicity : Iron deficiency, inflammatory bowel disease, gastric surgery : Metastatic carcinoma, leukemias, lymphomas, hepatic diseases, anemias, acute and chronic infection, inflammation, tissue damage : Pernicious anemia, malabsorption syndrome, liver disease, hypothyroidism : Acute hepatitis

Serum Iron

50-150 g/dl

60 - 80 g/dl

Ferritin

M 15 - 445 ng/ml F 10 - 235 ng/ml

10 - 310 ng/dl

Vitamin B12

200 - 900 pg/ml

150 pg/ml

Source: Brigden, 1999; Brigden & Heathcote, 2000; Kee, 2000; Tripp, 2000

changes in numbers (Thibodeau & Patton, 2004). The ability of the older adults body to respond to major blood loss by regenerating platelets may be inadequate, leading to inadequate clotting (Beers & Berkow, 2000) (see Table 1). The patient also must be assessed for potential or hidden blood losses, such as occult blood in stools and emesis. Erythrocyte sedimentation rate (ESR). Brigden (1999) noted that the erythrocyte sedimentation rate increases with age, but the cause of this increase is unknown. ESR measures the rate at which red blood cells (RBCs) settle in 1 hour. An annual rate of increase in time of sedimentation rate for older adults has been

quantified at 0.22 mm/hour/year from age 20 years (Duthie & Abbasi, 1991). An elevated ESR may indicate the presence of inflammation. Inflammation causes an alteration in blood proteins, making the RBCs heavier and causing them to settle faster (Fischbach, 2004). The acceptable reference range for the older adult is 40 mm/hour for males and 45 mm/hour for females (Brigden & Heathcote, 2000) (see Table 2). Because a slight elevation may or may not reflect the presence of an underlying inflammation, confirmation of a clinical problem may be difficult. Nurses should rely on other assessment factors, such as visible inflammation, pain, or fever, to determine a

possible clinical condition. Serum iron. Serum iron is decreased in many older adults, resulting in iron deficiency anemia as the most common form of anemia seen in older adults (Tripp, 2000) (see Table 2). One possible explanation is an agerelated decrease in hydrochloric acid (HCl) in the stomach (Beers & Berkow, 2000). HCI is important for facilitating iron absorption in the intestines. Serum iron, total iron-binding capacity, and iron stores decrease with age (Daniels, 2002). When there is a decrease in iron stores, serumferritin increases and serum transferrin decreases. The decrease in transferrin levels may indicate a decrease in liver syn-

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Table 3. Ge...

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