8.4 Cerebrospinal Fluid Analysis, Cell Counts & Cytology

ASCP Hematology Technologist Exam

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1 Chapter 1: Hematopoiesis & Cellular Physiology

1.1 Hematopoiesis, Bone Marrow Microenvironment & Growth Factors 1.2 Erythrocyte Physiology, Metabolism & Destruction Pathways 1.3 Leukocyte Kinetics, Morphology & Phagocytic Function 1.4 Platelet Physiology, Ultrastructure & Thrombopoiesis

2 Chapter 2: Erythrocyte Disorders & Non-Hemolytic Anemias

2.1 Iron Metabolism & Iron Deficiency Anemia 2.2 Anemia of Chronic Inflammation, Sideroblastic Anemias & Lead Toxicity 2.3 Hemoglobinopathies & Qualitative Globin Chain Defects 2.4 Alpha and Beta Thalassemias 2.5 Megaloblastic, Macrocytic & Hypoproliferative Anemias

3 Chapter 3: Hemolytic Anemias & Erythrocytosis

3.1 Intrinsic Hemolytic Anemias: Membrane & Metabolic Defects 3.2 Immune-Mediated Hemolytic Anemias & Paroxysmal Nocturnal Hemoglobinuria 3.3 Non-Immune Extrinsic Hemolytic Anemias & Microangiopathies 3.4 Polycythemia & Erythrocytosis Classification

4 Chapter 4: Benign Leukocyte Alterations, Acute Leukemias & Bone Marrow Evaluation

4.1 Quantitative Leukocyte Alterations, Toxic Change & Leukemoid Reaction 4.2 Inherited Leukocyte Anomalies, Reactive Lymphocytosis & Storage Disorders 4.3 Acute Myeloid Leukemia (AML) & Related Neoplasms 4.4 Acute Lymphoblastic Leukemia (ALL) & Precursor Lymphoid Neoplasms 4.5 Bone Marrow Examination, Differential & M:E Ratio Assessment

5 Chapter 5: Chronic Myeloid Neoplasms, MDS & Mature Lymphoid Neoplasms

5.1 Myelodysplastic Syndromes (MDS) & Overlap Syndromes 5.2 Chronic Myeloproliferative Neoplasms (CML, PV, ET, PMF) 5.3 Chronic Lymphocytic Leukemia & Indolent B-Cell Lymphomas 5.4 Aggressive Lymphomas, Hodgkin Lymphoma & Mature T-Cell Disorders 5.5 Plasma Cell Neoplasms & Monoclonal Gammopathies

6 Chapter 6: Hemostasis: Primary, Secondary & Fibrinolytic Systems

6.1 Primary Hemostasis, Platelet Receptors & Qualitative Platelet Disorders 6.2 Quantitative Platelet Disorders & Immune Thrombocytopenias 6.3 The Coagulation Cascade & Cell-Based Hemostatic Model 6.4 Fibrinolytic System, Natural Anticoagulants & Thrombophilia

7 Chapter 7: Factor Deficiencies, Coagulation Testing & Anticoagulation

7.1 Hereditary Coagulation Factor Deficiencies & von Willebrand Disease 7.2 Acquired Coagulation Factor Deficiencies, Circulating Inhibitors & DIC 7.3 Routine and Specialized Coagulation Testing & Mixing Study Interpretation 7.4 Anticoagulant Therapies, Laboratory Monitoring & Reversal Strategies 7.5 Viscoelastic Testing, Heparin Neutralization & Chromogenic Assays

8 Chapter 8: Hematology Laboratory Testing & Advanced Diagnostics

8.1 Automated Hematology Analyzers, Interference Flags & Manual Methods 8.2 Cytochemical Staining, Flow Cytometry & Molecular Diagnostics 8.3 Erythrocyte Sedimentation Rate, Hemolytic Indicators & Special Erythrocyte Studies 8.4 Cerebrospinal Fluid Analysis, Cell Counts & Cytology 8.5 Serous Effusions & Synovial Fluid Analysis

9 Chapter 9: Laboratory Operations, Quality Assessment & Safety

9.1 The Total Testing Process: Preanalytical, Analytical & Postanalytical Quality 9.2 Quality Control Statistics, Levey-Jennings Charts & Westgard Multirules 9.3 Laboratory Mathematics: Dilutions, Concentration, Molarity & Standard Curves 9.4 Method Evaluation, Diagnostic Statistics & Point-of-Care Testing 9.5 Regulatory Framework, Proficiency Testing & Competency Assessment 9.6 Laboratory Safety: Bloodborne Pathogens, Personal Protective Equipment & Chemical Hygiene 9.7 Emergency Response, Spill Management & Specimen Packaging and Transport 9.8 Hematology Instrumentation: Microscopy, Counters, Analyzers & Centrifuges

8.4 Cerebrospinal Fluid Analysis, Cell Counts & Cytology

Key Takeaways Explain This Topic AI

Cerebrospinal fluid is collected in four sequential sterile tubes: tube 1 chemistry and immunology, tube 2 microbiology, tube 3 hematology cell count and differential, tube 4 cytology or flow cytometry.

A traumatic tap shows red cells decreasing from tube 1 to tube 4, a clear supernatant, and possible clot formation; subarachnoid hemorrhage shows uniform red cell counts, xanthochromia, no clotting, and erythrophages or siderophages.

Clear CSF is counted UNDILUTED in the Improved Neubauer chamber using cells/uL = (cells counted x dilution factor x 10) / area counted in mm^2.

The ASCP BOC composite reference interval for CSF is 0 to 5 leukocytes and 0 red cells per microlitre; adult protein is 15 to 45 mg/dL and glucose is 60 to 70% of the simultaneous plasma value.

Bacterial meningitis gives marked neutrophilic pleocytosis with high protein and LOW glucose; viral meningitis gives a lymphocytic pleocytosis with NORMAL glucose; cells must be counted within about 1 hour because they lyse rapidly.

Last updated: August 2026

Cerebrospinal Fluid Analysis, Cell Counts & Cytology

The ASCP BOC includes body fluids inside BOTH the physiology content area and the laboratory testing content area, and the composite reference range table supplies CSF values (WBC and RBC 0 to 5 per microlitre) that examinees are expected to apply. Cerebrospinal fluid is the highest-stakes fluid the hematology bench handles: cell counts are performed manually on a very small, non-renewable volume, and the differential is prepared by cytocentrifuge.

Cerebrospinal Fluid (CSF) Analysis & Microscopic Cytology

Cerebrospinal fluid (CSF) is collected via lumbar puncture between the L3–L4 or L4–L5 intervertebral spaces. The standard diagnostic protocol utilizes a four-tube collection sequence to avoid pre-analytical contamination:

Tube 1: Chemistry and Immunology (Protein, Glucose, Electrophoresis, Oligoclonal bands).

Tube 2: Microbiology (Gram stain, Bacterial and Fungal cultures, Molecular PCR panels).

Tube 3: Hematology (Total cell count and cytospin differential count).

Tube 4: Specialized testing (Cytopathology, Flow cytometry, or reference infectious disease testing).

Adult CSF Reference Values vs. Neonatal Values

Adults: Total WBC count: 0 to 5 / μ L 0\text{ to }5/\mu\text{L} 0 to 5/ μ L (differential: 70 % ± 15 % 70\% \pm 15\% 70% ± 15% lymphocytes, 30 % ± 15 % 30\% \pm 15\% 30% ± 15% monocytes/macrophages, 0 % 0\% 0% neutrophils); RBC count: 0 / μ L 0/\mu\text{L} 0/ μ L ; Total Protein: 15 to 45 mg/dL 15\text{ to }45\text{ mg/dL} 15 to 45 mg/dL ; Glucose: 45 to 80 mg/dL 45\text{ to }80\text{ mg/dL} 45 to 80 mg/dL (representing 60 % to 70 % 60\%\text{ to }70\% 60% to 70% of simultaneous plasma glucose).

Neonates (0–28 days): Immature blood-brain barrier permits normal WBC counts up to 0 to 30 / μ L 0\text{ to }30/\mu\text{L} 0 to 30/ μ L (predominantly monocytes and lymphocytes) and protein levels up to 150 mg/dL 150\text{ mg/dL} 150 mg/dL .

Traumatic Tap versus Subarachnoid Hemorrhage (SAH) CSF HEMORRHAGE DIFFERENTIATION PROTOCOL
│
[ Grossly Bloody CSF Sample ]
│
┌────────────────────────┴────────────────────────┐
▼ ▼
[ Traumatic Lumbar Puncture ] [ Subarachnoid Hemorrhage ]
RBC count decreases markedly - RBC count remains uniform
from Tube 1 ──> Tube 4 across Tubes 1 through 4
Supernatant: Crystal Clear - Supernatant: Xanthochromic
post-centrifugation (pink/yellow within 2–12 hours)
Clotting: May form fibrin clot - Clotting: Non-clotting
Cytology: Intact fresh RBCs; - Cytology: Erythrophages &
no hemosiderin/siderophages hemosiderin-laden siderophages

Diagnostic Feature Traumatic Lumbar Tap (Venous Puncture) Subarachnoid Hemorrhage (True SAH)

Sequential Tube RBC Counts RBC counts decrease markedly from Tube 1 to Tube 4 RBC counts remain uniform across all four tubes

Centrifuged Supernatant Crystal clear / colorless Xanthochromic (pink/yellow due to oxyhemoglobin and bilirubin breakdown within 2–12 hours)

Clot Formation May form fibrin clots (plasma fibrinogen introduced from venous blood) Non-clotting (defibrinated within subarachnoid space)

Microscopic Cytology Fresh, intact discocytes; no macrophage phagocytosis Erythrophages (macrophages with engulfed RBCs) and siderophages (macrophages with dark hemosiderin/hematoidin granules)

Repeat Opening Pressure Normal Elevated ( > 200 mm H 2 O >200\text{ mm }\text{H}_2\text{O} > 200 mm H 2 O )
Meningitis CSF Differential Patterns

Acute Bacterial Meningitis: Markedly elevated WBC count ( > 1 , 000 to 10 , 000 + / μ L >1,000\text{ to }10,000+/\mu\text{L} > 1 , 000 to 10 , 000 + / μ L ) with > 80 % >80\% > 80% neutrophils ; marked protein elevation ( > 100 to 500 + mg/dL >100\text{ to }500+\text{ mg/dL} > 100 to 500 + mg/dL ); markedly decreased glucose ( < 40 mg/dL <40\text{ mg/dL} < 40 mg/dL or < 40 % <40\% < 40% of simultaneous plasma glucose); positive Gram stain/culture.

Viral (Aseptic) Meningitis: Moderately elevated WBC count ( 50 to 500 / μ L 50\text{ to }500/\mu\text{L} 50 to 500/ μ L ) with lymphocytic pleocytosis ( > 70 % – 90 % >70\%\text{--}90\% > 70% – 90% lymphocytes/reactive lymphocytes); normal glucose ( > 60 % >60\% > 60% plasma); normal to mildly elevated protein ( 50 to 100 mg/dL 50\text{ to }100\text{ mg/dL} 50 to 100 mg/dL ).

Fungal / Tubercular Meningitis: Moderate pleocytosis ( 100 to 500 / μ L 100\text{ to }500/\mu\text{L} 100 to 500/ μ L ) with mixed lymphocytes and monocytes ; markedly elevated protein ( > 100 to 500 mg/dL >100\text{ to }500\text{ mg/dL} > 100 to 500 mg/dL ); decreased glucose; positive India ink preparation or Cryptococcal Antigen (CrAg) lateral flow assay.

Manual CSF Cell Counting and the Dilution Calculation

CSF cell counts are performed on the undiluted fluid whenever the specimen is clear, using the Improved Neubauer hemocytometer. The general formula is the same one used for blood: Cells / μ L = Cells counted × Dilution factor × 10 Area counted (mm 2 ) \text{Cells}/\mu\text{L} = \frac{\text{Cells counted} \times \text{Dilution factor} \times 10}{\text{Area counted (mm}^2)} Cells / μ L = Area counted (mm 2 ) Cells counted × Dilution factor × 10

Undiluted clear fluid: count all nine large squares on both sides of the chamber. With an area of 18 mm 2 ^2 2 across both sides and a dilution factor of 1, the count is (cells x 10) / 18.

Turbid or bloody fluid: dilute with saline (for total cell counts) or with 3% glacial acetic acid (to lyse red cells for a leukocyte-only count), and multiply by the dilution factor.

Worked example. A clear CSF is counted undiluted; 36 leukocytes are seen across all nine squares of one side (area 9 mm 2 ^2 2 ). Cells/uL = (36 x 1 x 10) / 9 = 40/uL , a pleocytosis well above the 0 to 5/uL reference interval.

Correcting a Traumatic Tap

When blood contaminates the specimen, the leukocytes contributed by that blood must be subtracted before a true pleocytosis is reported. The simplest approach uses the patient's own peripheral blood ratio: WBC added = CSF RBC × Blood WBC Blood RBC \text{WBC added} = \text{CSF RBC} \times \frac{\text{Blood WBC}}{\text{Blood RBC}} WBC added = CSF RBC × Blood RBC Blood WBC

Subtract that value from the measured CSF WBC. Timing matters as well: cells in CSF deteriorate rapidly, so counts and cytospin preparations must be completed within 1 hour of collection, and the specimen is never refrigerated when culture is also requested.