NCLEX Review Guide: Adult Health - Immune System Laboratory Studies

White Blood Cell Count (WBC)

• Normal range: 4,000-11,000/μL - Elevated levels indicate infection, inflammation, or malignancy while decreased levels suggest immunosuppression or bone marrow disorders.
• Neutrophils (50-70%) are the first responders to bacterial infections and tissue damage. Neutropenia (<1,500/μL) places patients at high risk for life-threatening infections.
• Lymphocytes (20-40%) include T-cells and B-cells responsible for adaptive immunity. Elevated levels may indicate viral infections or hematologic malignancies.
• Monocytes (2-8%) transform into macrophages and are elevated in chronic infections and inflammatory conditions.

Serum Immunoglobulins

• IgG (700-1,500 mg/dL) provides long-term immunity and crosses placental barrier. Decreased levels indicate immunodeficiency while elevated levels suggest chronic infection or autoimmune disease.
• IgM (60-300 mg/dL) is the first antibody produced during acute infection. Elevated IgM indicates recent or acute infection.
• IgA (90-400 mg/dL) protects mucosal surfaces and is found in secretions like saliva and breast milk.
• IgE (<100 IU/mL) mediates allergic reactions and parasitic infections. Extremely elevated IgE levels may indicate anaphylaxis risk.

Acute Phase Reactants

• C-Reactive Protein (CRP) (<3.0 mg/L) rises rapidly within 6-12 hours of inflammation onset. CRP >10 mg/L indicates significant bacterial infection or tissue necrosis.
• Erythrocyte Sedimentation Rate (ESR) measures red blood cell settling rate with normal values varying by age and gender. Elevated ESR indicates inflammation but is non-specific and rises slowly.
• Procalcitonin (<0.25 ng/mL) is highly specific for bacterial infections. Levels >2.0 ng/mL indicate severe bacterial sepsis requiring immediate antibiotic therapy.

Antinuclear Antibodies (ANA)

• ANA titer (normal <1:80) screens for autoimmune disorders with higher titers indicating greater likelihood of autoimmune disease.
• Homogeneous pattern suggests systemic lupus erythematosus (SLE) while nucleolar pattern indicates scleroderma.
• Specific antibodies include Anti-dsDNA (specific for SLE) and Anti-Sm antibodies (highly specific for SLE).

ANA Testing Interpretation Steps

1. Check ANA titer - if negative, autoimmune disease unlikely
2. If positive, identify fluorescence pattern
3. Order specific antibody tests based on clinical presentation
4. Correlate results with patient symptoms and physical findings

Critical Nursing Considerations

• Always assess for signs of infection in neutropenic patients including fever, chills, or subtle changes in mental status as typical inflammatory responses may be absent.
• Monitor trends rather than single values - decreasing WBC with clinical improvement indicates effective treatment.
• Consider patient medications that may affect immune function including corticosteroids, chemotherapy, and immunosuppressants.