Interpreting Clinical and Laboratory Data

Interpreting Clinical Laboratory Tests

• Purpose: Evaluate general health, identify organ dysfunction, detect infection, shape care plan, monitor effectiveness.

Intro to Laboratory Medicine Disciplines

• Clinical Biochemistry: Analysis of blood, urine, bodily fluids.

• Hematology: Analyzes cellular components of blood.

• Clinical Microbiology: Analysis for infectious agents.

• Immunology: Focuses on autoimmune and immune deficiency diseases.

• Anatomic Pathology: Analysis of tissue for disease diagnosis.

Reference Range & Critical Test Value

• Reference Range: Sets boundaries and expected variability for analytes in healthy subjects, considering age, gender, race, ethnicity.

• Critical Test Value: Result significantly outside reference range, indicating pathophysiologic or life-threatening condition.

Complete Blood Count (CBC)

• Measures formed elements: Leukocytes (white blood cells), Erythrocytes (red blood cells), Thrombocytes (platelets).

White Blood Cell (WBC) Count

• Reference Range: $3.9-11.7 \times 10^{3}/mcL$

• Leukocytosis: WBC count above normal, common with infection, stress, trauma.

• Leukopenia: WBC count below normal, occurs with overwhelming infections, depressed immune system, bone marrow diseases.

Differential of WBC Count

• Determines number of each WBC type: Neutrophils, Lymphocytes, Eosinophils, Basophils, Monocytes.

• Neutrophils:

  • Relative Value: $40\%-75\%$; Absolute Value: $1.8-6.8 \times 10^{9}/L$

  • Abnormalities: Increased with bacterial infection/trauma; reduced with bone marrow diseases (<1.0 critical value).

  • Neutrophilia: Elevation of absolute neutrophils.

  • Bands: Immature neutrophils; Segs: Mature neutrophils. Elevation of both suggests severe bacterial infection.

• Lymphocytes:

  • Relative Value: $20\%-45\%$; Absolute Value: $1.0-3.4 \times 10^{9}/L$

  • Abnormalities: Increased with viral infections; reduced with immunodeficiency.

  • CD4 T lymphocytes: Absolute value less than $200$ diagnostic for HIV disease.

• Eosinophils:

  • Relative Value: $0\%-6\%$; Absolute Value: $0-0.4 \times 10^{6}/L$

  • Abnormalities: Increased with allergic reactions and parasitic infections.

• Basophils:

  • Relative Value: $0\%-1\%$; Absolute Value: $0-0.1 \times 10^{6}/L$

  • Abnormalities: Increased with allergic reactions.

• Monocytes:

  • Relative Value: $2\%-10\%$; Absolute Value: $0.2-0.8 \times 10^{6}/L$

  • Abnormalities: Increased with invasion of foreign material.

Red Blood Cell (RBC) Count

• Reference Range: Men: $4.4-5.9 \times 10^{6}/mcl$; Women: $3.8-5.2 \times 10^{6}/mcl$

• Anemia: Reduced RBCs, leads to reduced oxygen-carrying capacity. Treated with transfusion if severe (Hb <7.0 g/dL or Hct <21\%).

• Polycythemia: Abnormally elevated RBC count, often due to chronic low blood oxygen (e.g., high altitude, hypoxemic lung disease).

Hemoglobin (Hb) & Hematocrit (Hct)

• Hemoglobin: Bonds with oxygen.

  • Reference Range: Men: $13.3-17.7$ g/dL; Women: $11.7-15.7$ g/dL.

  • Microcytic Anemia: RBCs smaller with reduced hemoglobin.

  • Hypochromic Anemia: RBCs lack normal color.

• Hematocrit: Ratio of RBC volume to whole blood.

  • Reference Range: Men: $40\%-52\%$; Women: $35\%-47\%$.

  • Low levels with anemia/overhydration; high levels with polycythemia/dehydration.

Electrolyte Tests & Basic Chemistry Panel (BMP)

• Basic Concepts: Normal cellular function depends on fluid, electrolyte, acid-base homeostasis. Electrolytes are ions influencing enzymes.

• Interpretation: Blood samples are