Chapter Twenty Laboratory Values and the Older Adult
Meaning of Laboratory Values • Many normal ranges are different for older adults • Greater deviation from normal when under stress • Return to normal is slower • Relationship to clinical status • Lab values should be evaluated in relationship to individual’s entire clinical situation • Abnormal lab value may indicate a clinical stressor or medication side effect rather than illness
Meaning of Laboratory Values • Routine laboratory evaluations • Complete blood cell count • Serum glucose • Serum creatinine level • Serum electrolytes • Thyroid function tests • Urinalysis • Stool guaiac test
Common Screening Tests • Tuberculin skin test • Negative result <10 mm of induration • Screening method for tuberculosis • May need to be repeated 1 week later • Urinalysis • Appearance—clear yellow/straw • Specific gravity—1.005–1.020 • pH—4.5–8.0 • Negative for glucose, ketones, blood, bilirubin
Common Screening Tests • Urinalysis (cont.) • Types of specimens • Mid-stream clean catch • Fasting • 24-hour • Send specimen to lab within 10 minutes or keep refrigerated
Common Screening Tests • Stool for occult blood • Negative result—absence of test color • Test three specimens and two different sections of each stool • Avoid red meat, vitamin C intake, iron supplements, and aspirin 2 to 3 days before and during stool collection
Hematological Indicators • Complete blood count • Values do not change with age • Red blood cell count • Men—5.4 ± 0.9 × 1012/L • Women—4.8 ± 0.6 × 1012/L • Diagnose anemia, polycythemia, other bone marrow abnormalities
Hematological Indicators • Complete blood count (cont.) • Hemoglobin • Men—14–18 g/dL • Women—12–16 g/dL • Increase—polycythemia, dehydration • Decrease—anemia, recent hemorrhage, fluid retention, kidney disease
Hematological Indicators • Complete blood count (cont.) • Hematocrit • Men—47.0 ≠ 5.0% • Women—42.0 ≠ 5.0% • Measures percentage by volume or packed RBC in whole blood • Increased—polycythemia • Decreased—anemia, hemodilution, bone marrow disease
Hematological Indicators • Complete blood count (cont.) • RBC indices • MCV 90 ± 7 fl • MCH 29 ± 2 pg • MCHC 34 ± 2% • Aid in diagnosis and classification of anemias
Hematological Indicators • Complete blood count (cont.) • White blood cell count • 4.5–11.0 ×109/L • Used to identify infectious or inflammatory processes, monitor response to chemotherapy and radiation therapy • Increased—infection, leukemia, inflammation • Decreased—bone marrow depression, viral infection
Hematological Indicators • Complete blood count (cont.) • White blood cell differential • Neutrophils 1.8–7.7 ×109/L or 30%–60% • Eosinophils 0–0.45 ×109/L or 1%–4% • Basophils 0–0.20 ×109/L or 0%–0.5% • Lymphocytes 1.0–4.8 ×109/L or 25%–35% • Monocytes 0–0.8×109/L or 1%–4.0%
Hematological Indicators • Complete blood count (cont.) • White blood cell differential (cont.) • Used to determine severity of infection, detect allergic reactions, identify various leukemias
Hematological Indicators • Complete blood count (cont.) • Platelet count • 130,000–400,000/mL • Required for clot formation and hemostasis • Increased—iron-deficiency anemia, hemorrhage, malignancies, splenectomy • Decreased—bone marrow disease, folic acid or vitamin B12 deficiency, drug side effects
Hematological Indicators • Complete blood count (cont.) • Coagulation • Prothombin time • Normal: 9.5–11.8 s (control ±1 s) • Therapeutic: 1.5–2.0 times normal control • Determined before anticoagulation therapy and monitored throughout therapy
Hematological Indicators • Complete blood count (cont.) • Coagulation • Activated partial thromboplastin time (APTT) • Normal: 25–36 s • Therapeutic: 1.5–2.5 times normal control • Evaluated clotting factors of the intrinsic pathway
Blood Chemistry Indicators • Blood glucose • Fasting: • Normal: 75–115 mg/dL • Diabetes mellitus: 140 mg/dL on at least two occasions • Two hours after eating: • Normal: 140 mg/dL • Impaired glucose tolerance: 140–200 mg/dL • Diabetes mellitus: >200 mg/dl on at least two occasions
Blood Chemistry Indicators • Blood glucose (cont.) • Decreased—side effects of various medications, strenuous exercise • Increased—medication side effects, recent illness or infection • Electrolytes • Sodium • 136–145 mEq/L
Blood Chemistry Indicators • Electrolytes (cont.) • Sodium (cont.) • Hyponatremia • Caused by vomiting, diarrhea, renal disorders, diuretics, congestive heart failure • Hypernatremia • Caused by inadequate fluid intake, diarrhea, diuretics
Blood Chemistry Indicators • Electrolytes (cont.) • Potassium • 3.5–5.0 mEq/L • Hypokalemia • Caused by diuretics, malnutrition, vomiting, diarrhea • Hyperkalemia • Caused by renal failure, injuries, acidosis, diabetes mellitus, several medications
Blood Chemistry Indicators • Electrolytes (cont.) • Calcium 9–10.5 mg/dL • Hypocalcemia • Caused by hypoparathyroid, laxative, chemotherapy, corticosteroids • Hypercalcemia • Caused by hyperparathyroid, thiazide antidiuretics, immobilization, excessive vitamin D, calcium-containing antacids
Blood Chemistry Indicators • Electrolytes (cont.) • Phosphate 3–4.5 mg/dL • Chloride 98–106 mEq/L • End products of metabolism • Blood urea nitrogen (BUN) 10–20 mg/dL • Increased caused by renal disease, urinary tract obstruction, drugs
Blood Chemistry Indicators • End products of metabolism (cont.) • Blood urea nitrogen (cont.) • Decrease caused by severe liver failure, malnutrition, overhydration • Creatinine <1.5 mg/dL • Increase caused by renal disease, diabetic acidosis, starvation, diuretics • High levels indication of renal failure
Blood Chemistry Indicators • End products of metabolism (cont.) • Bilirubin • Total: 0.3–1.0 mg/dL • Direct: 0.1–0.3 mg/dL • Indirect: 0.2–0.7 mg/dL • Uric acid Men: 2.5–8.0 mg/dL Women: 1.5–6.0 mg/dL • Increase caused by loop diuretics, thiazides, starvation, alcohol abuse, chemotherapy
Blood Chemistry Indicators • Liver function tests • ALT 0–35 U/L • Increase caused by liver disease, medications, cholecystitis, trauma, lead ingestion • AST or SGOT 0–35 U/L • Increase caused by myocardial infarction, liver disease, hemolytic anemia, pulmonary emboli
Blood Chemistry Indicators • Liver function tests • LDH 60–100 U/mL
Nutritional Indicators • Protein indicators • Total serum protein 5.5–8.0 g/dL • Increase caused by dehydration, infection, diabetic acidosis, chronic alcoholism • Decreased caused by malnutrition, hepatic disease, renal disease, congestive heart failure • Albumin 3.5–5.5 g/dL • Increased caused by multiple myeloma • Decreased caused by malnutrition, liver and renal disease, collagen diseases, rheumatoid arthritis
Nutritional Indicators • Globulins 2.0–3.0 g/dL • Increase caused by tuberculosis, chronic syphilis, subacute bacterial endocarditis, myocardial infarction, diabetes mellitus • Iron indicators • Iron: Men 80–180 mg/dL Women 60–160 mg/dL • Essential in production and function of hemoglobin
Nutritional Indicators • Iron indicators (cont.) • Ferritin 15–200 ng/mL • Increased in hepatic disease, iron overload, leukemia, chronic renal disease • Decreased in chronic iron deficiency • Total iron-binding capacity • 250–460 mg/dL
Nutritional Indicators • Lipoproteins • Total plasma cholesterol • Desired <200 mg/dL • Borderline 200–239 mg/dL • High 240 mg/dL • High-density lipoprotein HDL • Desired >35
Nutritional Indicators • Lipoproteins • Low-density lipoprotein (LDL) • Desired 130 mg/dL • Borderline 130–159 mg/dL • High 160 mg/dL • Triglycerides • 160 mg/dL
Nutritional Indicators • Lipoproteins • Lipid abnormalities are often familial • Secondary causes • Diets high in saturated fat or cholesterol • Excessive alcohol intake • Estrogen supplements • Smoking • Sedentary lifestyle
Nutritional Indicators • Lipoproteins • Cholesterol is decreased in malnutrition, hyperthyroidism and chronic obstructive pulmonary disease
Drug Monitoring and Toxicology • Drug monitoring is important when toxic and therapeutic range is narrow • Commonly monitored drugs • Digoxin • Therapeutic: 0.5–20 ng/mL • Toxic: 2.5 ng/mL • Signs of toxicity • Visual changes, headache, nausea and vomiting, weakness and fatigue
Drug Monitoring and Toxicology • Commonly monitored drugs (cont.) • Theophylline • Therapeutic: 10–20 µg/mL • Toxic: 20 µg/mL • Signs of toxicity • Anorexia, abdominal discomfort, dizziness, shakiness, restlessness, palpitation, tachycardia, hypotension
Drug Monitoring and Toxicology • Commonly monitored drugs (cont.) • Phenytoin • Therapeutic: 10–20 µg/mL • Toxic: 30 µg/mL • Signs of toxicity • Drowsiness, mental confusion, tremors, photophobia, blurred vision
