In Depth Notes on Body Fluids in Hematology

BODY FLUIDS IN HEMATOLOGY

• Body fluids in the human body are typically sterile under normal conditions.
• During disease states, the quantity of body fluids can increase significantly, leading to effusions.
• Laboratory analysis includes counting white blood cells (WBCs), red blood cells (RBCs), performing differential counts on WBCs, and conducting chemistries and microbiology tests.
• Aliquots of body fluids are sent to respective departments for specific analyses.

CEREBROSPINAL FLUID (CSF)

• Functions of CSF:
  • Cushions and protects the brain and spinal cord.
  • Circulates nutrients, lubricates the central nervous system (CNS), and nourishes the brain tissue.
• Importance of Timeliness:
  • CSF must be delivered to the laboratory immediately (STAT) for analysis due to potential cell deterioration and glucose reduction.
• Normal Characteristics:
  • Clear and colorless fluid.

Indications for CSF Analysis:

• Meningitis, hemorrhage, neurologic diseases, leukemia diagnosis, and introduction of drugs like in subarachnoid hemorrhage.

Collection of CSF:

• Obtained via lumbar puncture, typically into 3-5 collection tubes:
  • Tube 1: Chemistry analysis.
  • Tube 2: Microbiology analysis.
  • Tube 3: Total Cell Count and differential.
  • Tube 4: Immunology/serology studies.
  • Tube 5: Further testing if required.
• Tubes 1 and 4 are particularly important in subarachnoid hemorrhage to differentiate between a bloody tap and true hemorrhage.

CSF-EXAMINATION

• Evaluation Parameters:
  • Tubes are assessed for color and appearance.
  • Turbidity may indicate presence of WBCs, bacteria, or protein.
  • Blood presence may signal hemorrhage; thus, both tubes are read to assess for differences.
  • Xanthochromia: Yellow tint indicates old subarachnoid hemorrhage and is a result of blood-brain barrier damage, leading to elevated protein levels.

CSF-CELL COUNTS

• Methods of Analysis:
  • Cell counts are performed using analyzers, but when not suitable (viscosity, debris), hemocytometers are employed.
• Hemocytometer Preparation:
  • Charge with 10 µL of sample, allow to sit in a moist environment, and read under microscopes at 10x (scan) and 40x (count).

Hemocytometer Dimensions:

• Depth of chamber: 0.1 mm.
• Dimensions of various squares help calculate volumes needed for cell counts:
  • Large square: 1 mm (Area = 1 mm²).
  • Medium square: 0.2 mm (Area = 0.04 mm²).
  • Smallest square: 0.05 mm (Area = 0.0025 mm²).

HEMOCYTOMETER-COUNTING GUIDELINES

• Count all nine squares if fewer than 200 cells are present.
• Count the four corner squares if more than 200 cells are present in total.
• In one square with excessive cells, count five squares within the center square.

CSF-RBC COUNTS

• Essential for diagnosing subarachnoid hemorrhage.
• Examples of RBC Calculations:
  • For counts <200 cells: Average counts in a sample. (Example Average = 12.5 from tube counts; calculated as $(12.5 / 0.9 = 13.9 imes 10^6/L)$).
  • For counts >200 cells: Use dilution factors. (Example Average = $(215 imes 20 / 0.4 = 10750 imes 10^6/L)$).

CSF-WBC COUNTS

• Crucial for diagnosing meningitis and monitoring leukemia progression.
• Normal Count: Should be less than or equal to 5 WBCs x $10^6/L$.
• Calculation Examples:
  • For counts <200 WBCs: Average counts from the sample to calculate (Example: $2.2 imes 10^6/L$).
  • For counts >200 WBCs: Use dilution factor for precision (Example: $10750 imes 10^6/L$).

HEMOCYTOMETER-READING

• Consistency in the reading pattern is essential to avoid missing cells.
• Focus on one type of cell at a time, avoid counting cells outside gridlines.

CSF-DIFFERENTIAL

• If WBCs are present on the hemocytometer, centrifuge CSF and create a smear on the sediment.
• Use a cytospin for better precision.
• Count 100 WBCs; differentials help identify infections (e.g., increased neutrophils for bacterial infections, increased lymphocytes for viral).

CSF-ADDITIONAL TESTING

• Chemistry:
  • Protein levels: Increased levels indicate infections, inflammation, or tumors; decreased levels signal CSF leaks.
  • Glucose testing: Typically low in bacterial/fungal infections and malignancies; remains normal in viral infections.
• Microbiology:
  • Gram staining, bacterial culture, PCR for viral meningitis, India ink for Cryptococcus, and VDRL for neurosyphilis.

SEROUS FLUIDS

• Includes fluids from pericardial, pleural, peritoneal, and dialysate sites.
• These fluids are continuously formed and reabsorbed; normally pale and yellow.
• Indications for Aspiration:
  • When turbid with increased volume, indicating infection/inflammation (effusion).
• Procedures:
  • Thoracentesis, paracentesis, and pericardiocentesis depending on the site.
• Lab procedures similar to those for serum, including cell counts and chemistry tests (protein, LDH, glucose, lipase, etc.).

CELL COUNTS- SERIOUS FLUIDS

• Count cells in EDTA serous fluids, either diluted or undiluted based on color.
• Methods mirror CSF counts utilizing the Neubauer hemocytometer.

SYNOVIAL FLUID

• Found in joint spaces, particularly the knees.
• Normal joints hold minimal fluid, and arthrocentesis is used to remove excess fluid.
• Characteristics:
  • Normal synovial fluid is straw-colored and viscous, typically containing few WBCs.
• Dysfunctions of RA and gout result in increased fluid and altered cell types.
• Tests for Crystal Identification:
  • Crystals distinguish gout and pseudogout using wet mounts.
• Differentiate from non-inflammatory/osteoarthritis conditions by WBC counts.

SCENARIO: LAB ANALYSIS CHALLENGES

• Thoroughly check samples:
  • Unlabeled samples require recollection.
  • Clotted CBC results may misrepresent platelet counts.
  • Smear and printout discrepancies need remaking to ensure matching.
  • Routine tests should be prioritized in emergency samples.
  • Monitoring the body's equilibrium post massive bleed reveals normal indices initially as bone marrow regulation takes time.