Anemia may be unnoticed if it is mild. - Academic Content Writers

Chapter 15
Laboratory and Diagnostic Tests

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Aging does not affect the life span of an erythrocyte, but replenishment after bleeding may be delayed due to a decrease in hematopoietic tissue in the marrow of the long bones.
Anemia may be unnoticed if it is mild.
Anemia symptoms include fatigue, shortness of breath, and paresthesia.
Chronic pulmonary disease or heart failure may led to overproduction of RBCs—polycythemia.
Red Blood Cells
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Hematocrit and hemoglobin values decline slightly after the age of 90.
Hemoglobin and Hematocrit
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Decrease in leukocytes may be related to drugs or severe infection.
Increase in leukocytes is generally seen with infections.
White cell count may be only moderately elevated in older adults with infection like pneumonia.
Other typical symptoms of infection such as fever, pain, and lymphadenopathy may be minimal or absent in older adults with infections, therefore look for sudden onset of confusion or lethargy.
Drugs can also cause an increase in leukocytes.

White Blood Cells
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4

Reduced effect on the bone marrow to release and store neutrophils
Impaired function of lymphocytes in vitro is suspected to cause a reduction in antibody response in later life.
Possibility of decline in monocyte function leading to increased susceptibility to infections and increased incidence of malignancies
Educating older adults about importance of participating in cancer screenings and maintaining immunizations throughout life are essential.
Effect of Aging on White Blood Cells
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5

Decrease in folic acid can indicate macrocytic anemia, megaloblastic anemia, and liver and renal disease.
Alcohol and various other drugs are known to interfere with absorption of folate.
Anticonvulsants, antimalarials, and methotrexate decrease folic acid levels.
Important to assess patients regarding their nutritional intake, including alcohol consumption habits
Elevated levels of folic acid may be seen in people with pernicious anemia.

Folic Acid
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Deficiency is caused by malabsorption secondary to gastric bypass, pancreatic disease, ileal resection or inflammation, prolonged use of certain medications, and strict vegan diets.
Malabsorption may be result from the effect of antibodies on gastric parietal cells and a decrease in intrinsic factor leading to pernicious anemia.
Prevalence of pernicious anemia increases significantly with aging.
Low B12 levels may cause fatigue, weakness, and memory loss.
Vitamin B12
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7

Serum iron levels show progressive decreases with advancing age.
Iron deficiency anemia is the most common form of anemia seen in older adults.
Anemia is not a normal consequence of aging.
Nurse should assess older adults for poor dietary intake of iron-containing foods and occult or chronic blood loss.
Iron
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8

Excreted by the kidneys
Estrogen thought to promote excretion of uric acid; elevated levels rarely seen in women before onset of menopause
Altered levels may result from faulty excretion, overproduction of uric acid, or presence of other substances that compete for excretion sites.
Elevated levels seen with gout
Thiazide diuretics, caffeine, low-dose aspirin, and antiparkinsonian drugs can also increase uric acid.

Uric Acid
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9

Increased PT seen in liver disease, vitamin K deficiency, bile duct obstruction, and salicylate intoxication
Medications that cause increase in PT: allopurinol, cephalothin, cholestyramine, clofibrate, and sulfonamides
Digitalis and diphenhydramine can cause decreased PT level.

Prothrombin Time (PT)
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Older adults are often prescribed the drug warfarin (Coumadin) after open-heart surgery and for chronic atrial fibrillation.
Adequacy of warfarin therapy can be assessed by following patient’s PT level.
The PT value is traditionally reported in seconds and includes a value called the international normalized ratio (INR).
INR should be between 2 and 3 for most thrombosis and between 3 and 4 for patients with history of recurrent thromboembolism or mechanical heart valves.
PT and Warfarin Therapy
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11

Heparin can inactivate prothrombin, so PTT is a good indicator of whether an older adult is receiving adequate anticoagulation therapy.
Nursing considerations include monitoring for bleeding and correct administration of the heparin dosage.

Partial Thromboplastin Time (PTT)
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Ordered when a person has symptoms of thrombus, embolus, or disseminated intravascular coagulation
Age, vascular disease, and kidney or hepatic disease may affect test results.
D-Dimer Test
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13

Indicates the presence of inflammation, so it is useful for monitoring the course of inflammatory activity in autoimmune diseases, infection, and cancers
Mild elevations may be associated with advancing age.
Due to the nonspecific nature of ESR values, interpret results in older adults in conjunction with subjective and objective findings on examination
Erythrocyte Sedimentation Rate
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Marker present in acute phase of an inflammatory response
CRP is useful in assessing patients with tissue injury (MI), autoimmune disease, or infection.
C-Reactive Protein
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15

Which of the following statements about laboratory results are true for the older adult patient?

Leukocytes may be only slightly elevated when infection is present.
Patients with rheumatoid arthritis who are taking methotrexate need folic acid supplements.
The most common type of anemia is pernicious anemia.
The patient with gout who is taking thiazide diuretics may have more attacks.
The therapeutic level of warfarin is assessed with the PTT.
Quick Quiz!
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ANS: A, B, D

Answer to Quick Quiz
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Decreases in platelet counts (to fewer than 100,000/mm3) require investigation.
Half of patient’s over age 60 diagnosed with low platelets have Myelodysplastic syndrome (MDS) which can progress to leukemia.
Spontaneous bleeding can occur when platelets are below 20,000/mm3.
When 40,000/mm3 or below, prolonged bleeding after procedures can occur.

Platelets
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18

Older adults may have serious problems with electrolyte imbalance.
Dehydration is the most common form of electrolyte disorder occurring in older adults.
Usually attributed to excess loss of water or altered fluid intake
Electrolytes
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Index of body water deficit or excess
Regulation maintains blood pressure, transmission of nerve impulses, and regulates body fluid levels in and out of cells.
Movement of sodium affects blood volume, which is tied to thirst mechanism and total body fluids.
Sodium
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Increases with age, related to the kidneys’ inability to excrete free water because of decreased basal levels of renin and aldosterone
Vague symptoms like malaise, confusion, headache, and nausea may progress to coma and seizures.
Determine whether an older adult has low sodium level but normal osmolarity; this is known as hypertonic hyponatremia
Excessive glucose, triglycerides, or plasma proteins in the blood cause normal or high osmolarity.

Hyponatremia
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Hypernatremia can occur from infusion of high-sodium solute fluids, excess water loss, and excessive diarrhea and decreased oral intake.
Symptoms are like those of hyponatremia, and the most common neurologic signs are lethargy, weakness, progressing to altered consciousness, and coma.
Hypernatremia
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22

Imbalances in older adults are caused by the same changes in the renal system as those affecting sodium.
Salt substitutes are high in potassium and should be used with caution especially with potassium sparing drugs which can lead to hyperkalemia.
Hypokalemia may be caused by gastrointestinal loss and the use of diuretics.
Potassium imbalance may predispose older adults to tachyarrhythmias and potentiate digitalis toxicity.

Potassium
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Hyperkalemia may cause muscle twitching, arrhythmias, and gastrointestinal symptoms.
Hypokalemia muscle weakness, confusion, and absence of bowel sounds
Signs and Symptoms of Hyperkalemia and Hypokalemia
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Closely tied to sodium
Losses and excesses in sodium affect chloride levels.
Chloride levels have not been shown to change with aging.
Chloride
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25

Changes in calcium regulation occur with aging but there is no alteration in serum calcium levels due to homeostasis.
Loss of calcium from bone maintains the normal level of calcium in the blood, but the resulting bone loss secondary to calcium leaching can lead to osteoporosis.
Calcium is protein bound with albumin so any change in albumin level also affects calcium.
Calcium has an inverse relationship with phosphorous.
Calcium
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26

Mineral found mostly in bone, in combination with calcium.
Phosphorus plays an important role in the maintenance of homeostasis.
Phosphorus levels are slightly decreased in comparison with younger adults.
Phosphorus
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27

Mineral important to enzyme action for production of energy
Most important sites of function are muscles (especially the heart) and nerves.
With aging, gastrointestinal absorption of magnesium decreases and excretion of magnesium by the kidneys increases, coupled with lower dietary intake can lead to hypomagnesemia.
Magnesium
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28

Four methods of diagnosing diabetes are: Fasting plasma glucose, oral glucose tolerance test, glycohemoglobin (hemoglobin A1c HbA1c), random blood sugar
Glucose metabolism alters with aging; reduced insulin effectiveness and islet cell dysfunction.
Higher incidence of diabetes in older adults
Hypoglycemia is harder to recognize, dizziness and visual disturbances are more common than palpitations and sweating.
Glucose
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29

Monitors nutritional status, liver and kidney disease
Albumin levels decrease with age
Levels <3.5 g/dL have been associated with increased mortality in hospitalized patients. Low albumin levels are also associated chronic disease including diabetes, hyperthyroidism, and HF. High albumin levels are associated with blood loss and dehydration. Albumin Copyright © 2019, by Elsevier Inc. All rights reserved. 31 Prealbumin is used to assess nutritional status. Measures protein status over the short term and is a more accurate measurement of malnutrition because of its short half-life of 1.9 days Plasma prealbumin level is useful in monitoring therapy with total parenteral nutrition. Prealbumin Copyright © 2019, by Elsevier Inc. All rights reserved. 32 Urea is major waste product of protein catabolism and a result of ammonia conversion in the liver, excreted by kidneys. Levels indicate both liver and kidney function. Values for older men are slightly higher than the adult normal levels of 7–22 mg/dL. In older women, BUN levels are also increased but at lower levels than for older men. Blood Urea Nitrogen (BUN) Copyright © 2019, by Elsevier Inc. All rights reserved. 33 End product of protein metabolism Rise in a patient’s BUN and creatinine levels indicates kidney disease. Physiologic decline in GFR does not cause a rise in creatinine level secondary to a decrease in muscle mass with aging. A creatinine level should not be considered an independent indicator of renal function, better to calculate creatinine clearance for a more realistic indication of renal function. Creatinine Copyright © 2019, by Elsevier Inc. All rights reserved. 34 Measure of GFR, estimated from serum creatinine and urine creatinine levels 24-hour urine test is required along with a serum level within the same 24-hour period. Creatinine clearance is a reflection of an older adult’s overall health status. It decreases an average of 6.5 mL/min each decade of life after age 20. Used to monitor medication response Creatinine Clearance Copyright © 2019, by Elsevier Inc. All rights reserved. 35 An optimal triglyceride level is 100 mg/dL or lower. Total cholesterol levels are a combination of LDL and HDL levels in the bloodstream. Total cholesterol levels be kept at less than 200 mg/dL. HDL, “good cholesterol” level >60 mg/dL is considered healthy, protects against heart disease.
LDL, “bad cholesterol” levels <70 mg/dL for risk of heart disease; <100 mg/dL for those at high risk but without established disease; <130 mg/dL for those at moderate risk for heart disease; <160 mg/dL for those at low risk for heart disease. Triglycerides and Cholesterol Copyright © 2019, by Elsevier Inc. All rights reserved. 36 Neurohormone secreted from cardiac ventricles in response to ventricular stretching and pressure overloading Help in diagnosis and treatment of patients with congestive heart failure (CHF) Values cannot be used to differentiate between systolic and diastolic heart failure. Brain Natriuretic Peptide Copyright © 2019, by Elsevier Inc. All rights reserved. 37 Testing for alkaline phosphatase (ALP) identifies liver and bone disorders, in older adults it’s used in the biochemical assessment of Paget disease and other bone diseases. Aspartate transaminase (AST) primarily used to diagnose liver disease Liver Enzymes Copyright © 2019, by Elsevier Inc. All rights reserved. 38 Troponin T and troponin I are the preferred tests for suspected heart attack. Appear 2–8 hours after cardiac injury and can remain elevated up to 2 weeks after a myocardial infarction Troponin Copyright © 2019, by Elsevier Inc. All rights reserved. 39 Includes assessment of two hormones secreted by the thyroid gland: thyroxine (T4) and triiodothyronine (T3) They are a screening tool for hypothyroidism or hyperthyroidism. T4 and T3 are generally elevated in hyperthyroidism and decreased in hypothyroidism. TSH is elevated in hypothyroidism and decreased in hyperthyroidism. Thyroid Function Tests Copyright © 2019, by Elsevier Inc. All rights reserved. 40 High levels of PSA may indicate the presence of prostate cancer, but an enlarged or inflamed prostate can also increase PSA levels. Patients need to understand the risks of testing for prostate cancer. Prostate-Specific Antigen (PSA) Copyright © 2019, by Elsevier Inc. All rights reserved. 41 Which of the following statements about laboratory results are true for the older adult patient? Hyperkalemia can cause digitalis toxicity. Hypernatremia may be related to laxative abuse. Albumin levels decrease with aging. The BUN level stays the same, but the creatinine level rises in renal failure. ALP is used to assess Paget’s disease. T3 and T4 are decreased in hypothyroidism. Quick Quiz! Copyright © 2019, by Elsevier Inc. All rights reserved. 42 ANS: B, C, E Answer to Quick Quiz Copyright © 2019, by Elsevier Inc. All rights reserved. 43 Protein in the urine (proteinuria) is an abnormal finding, means damage to the kidneys’ glomeruli. Glucose spills into the urine when blood glucose exceeds 180 mg/dL and with kidney damage or disease. Bacteriuria >100,000 colony-forming units (CFU) per milliliter of urine indicates infection.
Confusion, new onset of incontinence, lethargy, nocturia, and anorexia may be the first indication of underlying UTI.
Leukocytes in urine (pyuria) are more indicative of UTI.

Urinalysis (1 of 2)
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Positive leukocyte esterase indicates the need for microscopic examination and urine culture and sensitivity testing.
Nitrite test is used with leukocyte esterase to diagnose UTI.
Presence of ketones in urine occurs with diabetic ketoacidosis, a low-carbohydrate diet, starvation or fasting, and severe vomiting.
Urine pH reflects the body’s homeostatic state.
Hematuria is always an abnormal finding.

Urinalysis (2 of 2)
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Components of ABG testing are pH, oxygen, and carbon dioxide content, oxygen saturation, and bicarbonate level.
Be aware of supplemental oxygenation at the time of blood draw
Pulse oximetry is a reliable alternative to ABG testing and less invasive.
Decrease in chest wall recoil and in alveolar surface area, and less effective oxygen-to-carbon dioxide (CO2) exchange contribute to potential changes in oxygenation with aging.

Arterial Blood Gas (ABG) Testing
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Therapeutic drug monitoring is performed in older adults receiving drugs such as digoxin, theophylline, valproic acid, and phenytoin.
Therapeutic Drug Monitoring
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