Topic 3

Clinical Laboratory Studies Overview

  • Patients with lung disease often undergo numerous laboratory tests to assess their health status.

  • Common tests include:

    • Examination of formed elements in blood:

      • White Blood Cells (WBCs)

      • Red Blood Cells (RBCs)

      • Platelets

    • Serum plasma electrolyte examination.

Phases of Laboratory Testing

  1. Preanalytical Phase

    • Selection of appropriate assays for the patient's condition.

    • Patient identification and preparation.

    • Specimen selection, collection, and transport.

  2. Analytical Phase

    • Conducting actual testing performed by laboratory scientists.

  3. Postanalytical Phase

    • Reporting and interpretation of results.

Laboratory Test Parameters

Test Accuracy

  • True Positive (TP): Test is positive in a patient with the disease.

  • False Negative (FN): Test is negative in a patient with the disease.

  • True Negative (TN): A negative test in a disease-free patient.

  • False Positive (FP): A positive test occurs in a disease-free patient.

Sensitivity and Specificity

  • Sensitivity: Frequency of positive test results in patients with the disease.

  • Specificity: Frequency of negative test results in patients without the disease.

Hematology

  • Composition of Blood:

    • Cells: 45% (WBCs, RBCs, Platelets)

    • Plasma: 55% (90% water, salts, lipids, proteins).

  • Key Tests:

    • Complete Blood Count (CBC)

    • Tests assessing blood clotting ability.

Complete Blood Count (CBC)

  • Evaluates the number of circulating RBCs and WBCs, including their size and hemoglobin content.

Blood Components

  • Plasma: Rich in proteins (mainly albumin), immunoglobulins, clotting factors, and fibrinogen.

  • Functions of plasma include:

    • Transporting blood cells and nutrients.

    • Regulating water and mineral salts.

    • Providing defense against infections.

    • Coagulating blood.

Normal Blood Composition Breakdown

  • Decreased Blood Volume in Women: RBCs (37-43%), Men (43-49%).

  • Plasma includes proteins:

    • Albumins: 57%

    • Globulins: 38%

    • Fibrinogen: 4%

Reference Intervals for CBC

Component

Male

Female

WBC count

4.0-11.0 x 10^3/uL

4.0-11.0 x 10^3/uL

RBC count

4.20-6.00 x 10^6/uL

3.80-5.20 x 10^6/uL

Hemoglobin

13.5-18.0 g/dL

12.0-15.0 g/dL

Hematocrit

40-54%

35-49%

Platelet count

150-450 x 10^3/uL

150-450 x 10^3/uL

White Blood Cell (WBC) Count

  • Comprising various cells crucial for the immune response:

    • Neutrophils (60-70%)

    • Lymphocytes (20-25%): Key against viral infections and consist of T cells and B cells.

Classification of White Blood Cells

  • Myeloid Cells: Include neutrophils, eosinophils, mast cells, basophils, and monocytes.

  • Lymphoid Cells: Lymphocytes, divided into T cells and B cells.

Nonmalignant and Malignant White Blood Cell Abnormalities

  • Leukocytosis: Increased WBC count; Leukopenia: Decreased WBC count.

  • Abnormalities can indicate various conditions and are critical for diagnostic processes.

Red Blood Cell (RBC) Overview

  • Produced in bone marrow with a lifespan of about 120 days.

  • Function to carry oxygen via hemoglobin.

  • Anemia: Low RBC count; Polycythemia: Increased circulating RBCs.

Hemoglobin Function

  • Main component of RBCs, essential for oxygen transport and CO2 removal.

Platelet Count

  • Abnormalities such as thrombocytopenia can indicate bleeding risks.

Coagulation Screening Tests

  • Include:

    • Platelet count

    • APTT

    • PT/INR

    • D-dimer

Chemistry Panel

  • Basic metabolic panel includes:

    • Electrolytes

    • Glucose level

    • BUN (Blood urea nitrogen)

    • Creatinine

Importance of Electrolytes

  • Vital for homeostasis, muscle and nerve functions.

  • Imbalances often arise from renal failure, excessive intake, or loss.

Key Electrolytes

  • Sodium: Normal range (135-145 mEq/L); regulates fluid balance.

  • Potassium: Key intracellular cation (3.5-5.0 mEq/L); crucial for cardiac function.

  • Chloride: Extracellular anion, normal range (98-107 mEq/L).

  • Bicarbonate: Critical for acid-base balance.

Glucose Levels and Diabetes

  • Normal fasting levels (70-99 mg/dL); abnormal levels indicate hyperglycemia or hypoglycemia.

  • Diabetes Mellitus Type 1 vs. Type 2:

    • Type 1: Insulin-deficient; Type 2: Insulin-resistant.

Renal Function Tests

  • BUN and creatinine are primary markers for assessing kidney function.

Urinalysis

  • Assesses physical, chemical, and microscopic characteristics of urine.

Hepatic Panel

  • Tests for proteins and liver-associated enzymes to assess liver health.

Lipid Panel

  • Evaluates cholesterol levels and associated health risks.

Cardiac Biomarkers

  • Include CK, CK-MB, myoglobin, troponin, and BNP for diagnosing cardiac events.

Microbiology

  • Involves isolation and identification of pathogens; sputum samples are critical for diagnosis.

Laboratory Testing for Respiratory Conditions

  • Various tests related to lung disease provide crucial diagnostic information.