Diagnostic Testing

CHAPTER 34 Diagnostic Testing

NORMAL STRUCTURE AND FUNCTION OF BLOOD CELLS

  • Learning Objective 34.1: Identify the normal structure and function of blood cells.

    • Blood is composed of various cell types, including:

    • Erythrocytes:

      • Function: Carry oxygen via hemoglobin (Hgb).

      • Measurement: Normal counts vary with age and gender.

    • Thrombocytes (Platelets):

      • Function: Play a crucial role in hemostasis and blood clotting.

    • Leukocytes:

      • Function: Defend against infections and foreign materials.

      • Types:

      • Lymphocytes: (Types of white blood cells)

        • Function: Recognize foreign antigens and produce antibodies.

      • Monocytes:

        • Function: Involved in phagocytosis and mature into macrophages.

      • Eosinophils:

        • Function: Destroy parasites and mediate allergic reactions.

      • Neutrophils:

        • Function: First responders to bacterial infections.

      • Basophils:

        • Function: Involved in inflammatory responses, releasing histamine.

PLASMA

  • Definition: The liquid component of blood, consisting of water, electrolytes, nutrients, hormones, and proteins.

  • Major Proteins:

    • Albumin: Maintains oncotic pressure, transports substances.

    • Fibrinogen: Involved in blood clotting.

    • Globulins: Include antibodies, contribute to immune response.

LABORATORY TESTS: BLOOD

  • Learning Objective 34.2: Identify common blood tests, their purposes, and their normal values.

    • Complete Blood Count (CBC): Evaluates elements of blood; includes hemoglobin and hematocrit measurements.

    • Coagulation Studies:

    • Prothrombin Time (PT): Measures the extrinsic pathway of coagulation.

    • Activated Partial Thromboplastin Time (APTT): Measures intrinsic pathway.

    • Differential White Blood Cell Count (see Table 34.1):

    • Neutrophils (55-70%): First line of defense.

    • Lymphocytes (20-40%): Antibody production.

    • Monocytes (2-8%): Phagocytosis.

    • Eosinophils (1-4%): Allergic disease and parasitic infections.

    • Basophils (0.5-1%): Release histamines in inflammatory responses.

COMPLETE BLOOD COUNT

  • Hematocrit: Percentage of red blood cells in blood.

    • Normal Values:

    • Adult Male: 42-52%

    • Adult Female: 37-47%

    • Decreased Levels Indicate: Anemia, bone marrow suppression, chronic disease.

COAGULATION STUDIES

  • Components:

    • Prothrombin Time (PT): Normal: 11-12.5 seconds

    • International Normalized Ratio (INR): Used for patients on anticoagulation therapy (Normal: 0.8-1.1).

    • Activated Partial Thromboplastin Time (APTT): Normal: 30-40 seconds

COMPLETE BLOOD COUNT (CBC) TABLE

Component

Normal Value

Abnormal Values

RBCs (million/µL)

Adult Male: 4.7-6.1, Female: 4.2-5.4

Anemia, Bone marrow suppression

Hemoglobin (g/dL)

Male: 14-18, Female: 12-16

Similar to RBCs above

Hematocrit (%)

Male: 42-52, Female: 37-47

Similar to above

WBC (cells/mm3)

Adult: 5000-10,000

Chronic leukemia, infections

BLOOD CHEMISTRY

  • Focuses on cations and anions, includes basic metabolic panel (BMP).

    • Basic Metabolic Panel Components:

    • Sodium: Normal 136-145 mEq/L

    • Potassium: Normal 3.5-5 mEq/L

    • BUN: Normal 10-20 mg/dL

    • Serum Creatinine: Males: 0.6-1.3 mg/dL, Females: 0.5-1.1 mg/dL.

KIDNEY FUNCTION TESTS

  • Measured by BUN and Creatinine.

LIPID PROFILE

  • Components:

    • Total Cholesterol: <200 mg/dL is optimal.

    • LDL: <130 mg/dL for low risk.

    • HDL: >45 mg/dL for males, >55 mg/dL for females.

    • Triglycerides: Normal 40-160 mg/dL (Males), 35-135 mg/dL (Females).

CARDIAC MARKERS AND TESTS

  • Total Creatine Kinase (CK): Elevation indicates muscle damage.

  • Troponin Levels: Specific to cardiac muscle damage, used as a marker for myocardial infarction.

URINALYSIS

  • Purpose: Evaluates health conditions of the urinary tract.

  • Normal Values for Components:

    • Glucose: Negative; Present in diabetes mellitus.

    • Ketones: Negative; Present in fasting states.

    • Protein: Negative; Present in renal disease.

COMMUNICATION OF TEST RESULTS

  • Importance of communicating test results to patients and team members in a timely manner. Nurses must adhere to patient safety protocols and HIPAA regulations regarding results dissemination.

NURSING DIAGNOSES ASSOCIATED WITH DIAGNOSTIC TESTING

  • Nursing Diagnosis often includes:

    • Anxiety

    • Risk for injury

    • Knowledge deficit regarding procedures.

NURSING CARE GUIDELINES

  • Follow standard precautions during specimen collections.

  • Ensure informed consent is obtained and that all proper protocols for documentation and specimen handling are followed to provide optimal patient outcomes.