Synovial Fluid Analysis Flashcards

Vocabulary-style flashcards covering the components, characteristics, classifications, and analysis of synovial fluid based on Chapter 11.

Synovial membrane

The tissue that filters plasma to form synovial fluid and contains synoviocytes.

Diarthroses

Movable joints that use synovial fluid for lubrication.

Synovial fluid functions

Provides lubrication for movable joints and lessens the shock of joint compression.

Synovial fluid formation

Formed as an ultrafiltrate of plasma across the synovial membrane plus hyaluronic acid.

Synoviocytes

Cells in the synovial membrane that secrete hyaluronic acid to make the fluid viscous.

Hyaluronic acid

A substance secreted by synoviocytes that provides viscosity and lubrication to joint fluid.

Noninflammatory joint disorders

A classification of arthritis that includes degenerative conditions and osteoarthritis.

Osteoarthritis

A specific noninflammatory, degenerative joint disorder.

Inflammatory joint disorders

A classification including immunologic diseases like lupus erythematosus (LE), rheumatoid arthritis (RA), and Lyme disease.

Lupus erythematosus (LE)

An immunologic, inflammatory joint disorder.

Rheumatoid arthritis (RA)

An immunologic, inflammatory disorder characterized by persistent joint inflammation.

Lyme disease

An inflammatory disorder where arthritis is a frequent complication; tested via Borrelia burgdorferi antibodies.

Crystal-induced disorders

Joint disorders such as gout and pseudogout caused by the presence of crystals.

Gout

A crystal-induced disorder associated with monosodium urate (MSU) crystals.

Pseudogout

A crystal-induced disorder associated with calcium pyrophosphate dihydrate (CPPD) crystals.

Septic joint disorders

Joint disorders caused by microbial infection.

Hemorrhagic joint disorders

Joint disorders caused by trauma, tumors, or coagulation deficiencies.

Normal Synovial Volume

$$<3.5\,mL$$

Normal Synovial Color

Colorless to pale yellow.

Normal Synovial Clarity

Clear.

Normal Synovial Viscosity

Able to form a string $4\,to\,6\,cm$ long.

Normal Leukocyte count

<200\,cells/\mu L

Normal Neutrophil differential

$<25\%$ of the differential.

Normal Glucose:plasma difference

$<10\,mg/dL$ lower than the blood glucose level.

Arthrocentesis

A needle aspiration procedure used to collect synovial fluid.

Normal knee fluid amount

$$3.5\,mL$$

Inflamed knee fluid amount

>25\,mL

Specimen clotting

Normal fluid does not clot, but diseased fluid may clot.

Tube #1

No anticoagulant tube used for chemical and immunologic studies.

Tube #2

Anticoagulant tube (liquid EDTA) used for microscopic and hematology studies.

Tube #3

Sterile heparinized or anticoagulant tube used for microbiological studies.

Sodium fluoride

Additive used for synovial fluid glucose testing to prevent cellular metabolism.

Testing urgency

Test ASAP to avoid cellular lysis and changes in crystals.

Deep yellow with green tinge

A synovial fluid appearance indicating infection.

Red synovial fluid

Indicates hemorrhagic fluid or a traumatic tap.

Traumatic tap identification

Look for decreasing blood in successive collection tubes.

Milky synovial fluid

Usually indicates a crystal-induced disorder.

Synovial Turbidity

Caused by white blood cells (WBCs), cellular debris, or fibrin.

Polymerization of hyaluronic acid

Essential for joint movement and providing synovial viscosity.

Mucin Clot Test

Performed using $2\%$ acetic acid to confirm fluid is synovial by forming a hyaluronate clot.

Mucin Clot Reagent ratio

1 part fluid diluted with 4 parts $2\%$ acetic acid.

Cell Count Diluent

Use normal saline/methylene blue; do not use normal WBC diluting fluid.

Hyaluronidase

Enzyme used to treat viscous fluid to facilitate cell counting and cytocentrifugation.

Hemocytometer

Counting chamber used to perform synovial white blood cell counts.

Sepsis WBC count

May reach $>100,000\,cells/\mu L$.

Normal Lymphocyte percentage

$\sim 70\%$ of the differential count.

Normal Monocyte percentage

$\sim 30\%$ of the differential count.

LE cells

Neutrophils that have ingested the altered nucleus of another cell, seen in lupus.

Reiter cells (neutrophages)

Vacuolated macrophages that have ingested neutrophils.

Ragocytes (RA cells)

Neutrophils with small, dark granules containing RA factor (IgM).

Lipid droplets

Sometimes seen in synovial fluid following crush injuries.

Hemosiderin granules

Pigment granules that may be found in synovial cytology.

Monosodium urate (MSU)

Crystal found in gout; needle-shaped and negatively birefringent.

Calcium pyrophosphate dihydrate (CPPD)

Crystal found in pseudogout; rhomboid-shaped and positively birefringent.

MSU causes

Impaired purine metabolism, high purine foods, leukemia chemotherapy, or decreased renal excretion.

CPPD causes

Degenerative arthritis or disorders causing elevated calcium levels (calcification).

Parallel MSU orientation

Crystals appear yellow under compensated polarized light.

Perpendicular MSU orientation

Crystals appear blue under compensated polarized light.

Parallel CPPD orientation

Crystals appear blue under compensated polarized light.

Perpendicular CPPD orientation

Crystals appear yellow under compensated polarized light.

Cholesterol crystals

Observed in persistent inflammatory processes like rheumatoid arthritis.

Corticosteroid crystals

Flat, variable plates found following joint injections.

Calcium oxalate crystals

Found in synovial fluid of renal dialysis patients.

Crystal Artifacts

Includes starch, powdered anticoagulants, dust, and scratches.

Normal synovial protein

Less than $3\,g/dL$.

Increased protein significance

Seen in inflammatory and hemorrhagic categories.

Synovial Glucose (Normal)

Not less than $10\,mg/dL$ of the plasma glucose level.

Markedly decreased glucose

A finding associated with the inflammatory and septic categories.

Microbiology Routine Tests

Gram stain and cultures.

Borrelia burgdorferi

The causative agent of Lyme disease, for which serum is usually tested.

Osteoarthritis Color/Clarity

Yellow and Clear.

Osteoarthritis WCC

$$700\,cells/\mu L$$

Osteoarthritis Neutrophils (%)

$$15\%$$

Traumatic arthritis Color/Clarity

Straw and Cloudy.

Traumatic arthritis WCC

$$1000\,cells/\mu L$$

Traumatic arthritis Neutrophils (%)

$$25\%$$

SLE Synovial Color/Clarity

Straw and Clear.

SLE WCC

$$2000\,cells/\mu L$$

SLE Neutrophils (%)

$$30\%$$

Rheumatoid Factor (RF) Color/Clarity

Yellow and Slightly Cloudy.

RF WCC

$$14000\,cells/\mu L$$

RF Neutrophils (%)

$$50\%$$

Pseudogout WCC

$$15000\,cells/\mu L$$

Pseudogout Neutrophils (%)

$$70\%$$

Gout Color/Clarity

Yellow to milky and Cloudy.

Gout WCC

$$20000\,cells/\mu L$$

Gout Neutrophils (%)

$$70\%$$

RA Synovial Color/Clarity

Yellow to green and Cloudy.

RA WCC

$$20000\,cells/\mu L$$

RA Neutrophils (%)

$$70\%$$

Infective arthritis (TB) Color/Clarity

Yellow and Cloudy.

Infective arthritis (TB) WCC

$$20000\,cells/\mu L$$

Septic arthritis Color

Grey or bloody.

Septic arthritis Clarity

Turbid.

Septic arthritis WCC

$$90000\,cells/\mu L$$

Septic arthritis Neutrophils (%)

$$90\%$$

Non-inflammatory WCC range

$$<2000\,cells/\mu L$$

Inflammatory WCC range

$$2,000\,to\,50,000\,cells/\mu L$$

Septic WCC range

$$>50,000\,cells/\mu L$$

Birefringence negative, needle-shaped

Urate (MSU) crystals.