copyright © 2014. f.a. davis company chapter 11 synovial fluid

Copyright © 2014. F.A. Davis Company

CHAPTER 11CHAPTER 11

SYNOVIAL FLUIDSYNOVIAL FLUID


Upon completing this chapter, the reader will be able to1.Describe the formation and function of synovial fluid.2.Relate laboratory test results to the four common classifications of joint disorders.3.State the five diagnostic tests most routinely performed on synovial fluid.4.Determine the appropriate collection tubes for requested laboratory tests on synovial fluid.5.Describe the appearance of synovial fluid in normal and abnormal states.6.Discuss the normal and abnormal cellular composition of synovial fluid.

Learning ObjectivesLearning Objectives


7. List and describe six crystals found in synovial fluid.8. Explain the differentiation of monosodium urate and calcium

pyrophosphate crystals using polarized and compensated polarized light.

9. State the clinical significance of glucose and lactate tests on synovial fluid.

10. List four genera of bacteria most frequently found in synovial fluid.

11. Describe the relationship of serologic serum testing to joint disorders.

Learning Objectives Learning Objectives (cont’d)(cont’d)


• Synovial fluid functions– Lubrication for the movable joints: diarthroses– Nutrients for articular cartilage– Lessens shock of joint compression

• Formation – Ultrafiltrate of plasma across synovial membrane– No high weight molecules– Synoviocytes in synovial membrane secrete hyaluronic

acid that makes the fluid viscous (lubrication)

PhysiologyPhysiology


AnatomyAnatomy


• Four classifications of disorders (arthritis)1. Noninflammatory: degenerative, osteoarthritis2. Inflammatory: immunologic, lupus erythematosus

(LE), rheumatoid arthritis (RA), Lyme disease• Crystal-induced, gout and pseudogout

3. Septic: microbial infection4. Hemorrhagic: trauma, tumors, coagulation

deficiencies

DisordersDisorders


Table 11–1 Synovial Fluid Reference Values2

Volume <3.5 mLColor Colorless to pale yellow

Clarity ClearViscosity Able to form a string 4 to 6 cm

longLeukocyte count <200 cells/µLNeutrophils <25% of the differential

Crystals None presentGlucose:plasma difference <10 mg/dL lower than the blood

glucose levelTotal protein <3 g/dL

Classification and Pathologic Classification and Pathologic Significance of Joint Disorders Significance of Joint Disorders


• Needle aspiration called arthrocentesis• Normal knee fluid amount 3.5 mL

– >25 mL if inflamed• Normal fluid does not clot; diseased fluid clots• Collect in

– Sterile heparinized or SPS for microbiology– Liquid EDTA (no powdered) for hematology– Heparinized or nonanticoagulated for other tests– Centrifuge nonanticoagulated tube and separate– Sodium fluoride for glucose

• Test ASAP to avoid cellular lysis and changes in crystals

Specimen Collection Specimen Collection & Handling& Handling


• Normal: clear and pale yellow (egg white)• Deeper yellow with noninflammatory and

inflammatory; green tinge = infection• Hemorrhagic or traumatic tap = red• Traumatic tap: look for decreasing blood in tubes• Crystal induced: milky• Turbidity: white blood cells (WBCs) or cellular debris,

fibrin

AppearanceAppearance


• Polymerization of hyaluronic acid– Essential for joint movement

• Arthritis decreases polymerization• 4 to 6 cm string from aspirating needle = OK• Ropes (mucin clot test)

– Add fluid to 2% to 5% acetic acid to form clot– Rate, good: solid clot; clear fluid, fair: soft formed clot;

low: friable clot; poor: no clot• Use acetic acid to identify synovial fluid

ViscosityViscosity


• WBCs most common• Do not use normal WBC diluting fluid; use normal

saline/methylene blue• May have to treat viscous fluid with hyaluronidase

or 37°C incubation first• Perform on a Neubauer counting chamber

– Automated instrument, may need more hyaluronidase

• Normal: <200 WBCs/μL, septic may reach >100,000

Cell CountsCell Counts


• Line petri dish with moist filter paper.• Place hemocytometer on two small sticks above paper.• Fill both sides of the hemocytometer for compatibility. • For counts less than 200 WBCs/μL, count all nine large

squares.• For counts greater than 200 WBCs/μL in the above count ,

count the four corner squares.• For counts greater than 200 WBCs/μL in the above count,

count the five small squares used for a RBC count.2<<AU: What does superscript 2 refer to?>>

Counting ProcedureCounting Procedure


• Incubate with hyaluronidase, then cytocentrifuge• Normal cells: monocytes, macrophages, synovial

tissue cells• Neutrophils: <25%, increase in sepsis • Lymphocytes: <15%, noninflammatory higher• All cells may appear more vacuolated

Differential CountDifferential Count


• Other cells– LE cells – Eosinophils– Reiter cells/neutrophages: vacuolated macrophages with

ingested neutrophils– Ragocytes (RA cells): neutrophils with small, dark

granules containing RA factor (IgM)– Lipid droplets: crush injuries– Hemosiderin granules: pigmented villonodular synovitis

Differential Count Differential Count (cont’d)(cont’d)


• Important diagnostic test; frequently performed• Acute and chronic cases• Metabolic disorders and decreased renal

function• Other causes: increased blood levels,

degeneration of bone and cartilage, injection of corticosteroids

Crystal IdentificationCrystal Identification


• Primary: monosodium urate (MSU) in gout; calcium pyrophosphate dihydrate (CPPD) in pseudogout

• MSU: impaired purine metabolism, high purine foods, leukemia chemotherapy, decreased renal excretion of uric acid

• CPPD: degenerative arthritis, disorders causing elevated calcium levels

Types of CrystalsTypes of Crystals


• Hydroxyapatite: cartilage degeneration, only seen with electron microscopy

• Cholesterol: systemic autoimmune diseases (LE, RA) appear similar to urine cholesterol crystals: notched corners

• Corticosteroids: injections, flat, variable plates• Calcium oxalate: renal dialysis patients• Artifacts: starch, powdered anticoagulants, dust,

scratches (clean slides, cover slips)

Types of Crystals Types of Crystals (cont’d)(cont’d)


Slide PreparationSlide Preparation

• Examine ASAP– Crystal changes, MSU and

CPPD are seen intracellularly and cells disintegrate

• Initial examination is wet preparation unstained under low and high power

• Crystals may be seen on differential


• Continued examination is done under polarized and compensated polarized light of wet preparation

• MSU crystals: needle shaped; seen intra- and extracellularly; may be seen sticking through cytoplasm

• CPPD crystals: rhombic, square shaped, or short rods; often seen in vacuoles of neutrophils; MSU crystals lyse vacuole membranes

Slide ExaminationSlide Examination


Crystal PolarizationCrystal Polarization

• Both MSU and CPPD crystals polarize light

• MSU is highly birefringent and appears brighter than CPPD

• Confirm identification using compensated polarized light


• Red compensated polarized light: red compensator is placed between crystal and analyzer, producing a red background

• Separates light into slow- and fast-moving vibrations• Align crystals with slow vibration• Linear structure of molecules causes different colors

to be produced

Compensated Polarized LightCompensated Polarized Light


MSU and CCPD Crystals Under MSU and CCPD Crystals Under Compensated Polarized LightCompensated Polarized Light


MSU and CPPD Under MSU and CPPD Under Compensated LightCompensated Light


MSU Under Compensated LightMSU Under Compensated Light

• MSU molecules run parallel to the long axis, aligned with slow vibration; fast light is impeded, producing a yellow color (negative birefringence)

• CPPD molecules run perpendicular to long axis and impede the slow light producing a blue color (positive birefringence)


• As an ultrafiltrate of plasma, normal values are similar to those of plasma

• Few are clinically important• Most frequent is glucose

– Normal: not less than 10 mg/dL of plasma glucose– Draw sample same time as fluid is collected– Markedly decreased levels seen in inflammatory and

septic categories

Chemistry TestsChemistry Tests


• Synovial fluid protein– Normal is less than 3 g/dL

• Increased in inflammatory and hemorrhagic categories

• Synovial fluid lactate and acid phosphatase• Severity and prognosis of rheumatoid arthritis

(RA)

Chemistry Tests Chemistry Tests (cont’d)(cont’d)


• Volume: <3.5 mL• Color: colorless to pale yellow• Clarity: clear• Viscosity: able to form a string 4 to 6 cm long• Leukocyte count: <200 cells/μL• Neutrophils: <25% of the differential• Crystals: none present• Glucose: <10 mg/dL lower than the blood glucose plasma

difference • Total protein: <3 g/dL

Reference Synovial Fluid Values Reference Synovial Fluid Values


• Infections caused by inflammation, trauma, and systemic infections

• Gram stain and cultures are routinely performed• Culture must include chocolate agar

– Primary organisms are Staphylococcus, Streptococcus, Haemophilus influenzae, and Neisseria gonorrhoeae

– Patient history determines fungal and Tuberculosis (TB) cultures

Microbiology TestsMicrobiology Tests


• Majority of related tests are performed on serum and fluid may only serve as a confirmation

• RA and LE are the most common autoimmune causes of arthritis

• Lyme disease: arthritis is frequent complication; test serum for Borrelia burgdorferi antibodies

• Extent of inflammation: test for C-reactive protein and fibrinogen

Serologic TestsSerologic Tests

copyright © 2014. f.a. davis company chapter 11 synovial fluid

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