Chapter 12 - Synovial Fluid

Synovial fluid = “ “

Joint fluid

Synovial fluid is found in…

diarthroses

Synovial fluid functions

lubrication of joints, nutrients for articular cartilage, lessens shock of joint compression

Synoviocytes (A and B)

A = macrophage like, superficial

B = fibroblast like, deep

Is SF a plasma ultrafiltrate

Yes

What MPS is found in SF

Hyaluronic acid

Arthritis

Damage to articular membranes produced pain and stiffness in the joints

What tests are commonly performed on SF

WBC count, Differential, Gram stain, Culture, Crystals

What are the 4 classifications of arthritis

I = noninflammatory = degenerative, osteoarthritis

II = inflammatory = SLE, RA

III = Septic = microbial infection

IV = Hemorrhagic = trauma, tumors, hemophilia, coagulation deficiencies

SF collection is termed

Arthrocentesis

joint by needle aspiration

Normal adult knee fluid amount

<3.5 mL

>25 mL = inflammation

Does normal SF clot

no

diseased fluid clots

SF tube collection order

Tube 1 = Red top = Chemistry/Immunology

Tube 2 = Green/Lavender top = Hematology

Tube 3 - Green/Yellow top = Microbiology

All tubes have ~4-5 mL SF fluid

test ASAP to avoid cellular lysis and changes in crystals

Normal SF color and clarity

clear and pale yellow (egg white)

Yellow SF indicates

inflammatory and noninflammatory effusions

Green SF indicates

bacterial infection

SF traumatic tap

uneven blood distribution

factors affecting SF clarity

WBCs, RBCs, synoviocytes, crystals, fat droplets, fibrin, cellular debris

Turbid SF indicates

WBC*

cell debris.fibrin

Mily SF indicates

crystals

SF viscosity contributed by

Hyaluronic acid

• arthritis decreases polymerization

Normal SF viscosity

4-6 cm string from aspirating needle

SF viscosity, mucin clot test

2-5% acetic acid

Good = solid clot

Fair = soft clot

Low = friable clot

Poor = no clot

SF cell counts must be done ASAP or preserved by

refrigeration

What diluting agent is used with SF cell counts

saline / methylene blue

Normal SF WBC count

<200 cells/uL

> 100,000 WBC / uL in SF indicates

severe infection (may be septic)

If SF is too viscous for cell counts what do you do

treat with one drop 0.05% hyaluronidase or 37 incubation

SF cell count procedure

For counts <200, count all nine large squares

for counts >200 in above count, count the four corner squares

for counts >200 in above count, count the five small RBC squares

SF Differential counts mainly what cells

mainly monocytes, macrophages, SF tissue cells

Normal % neutrophils and lymphocytes in SF

Neutrophils < 25%

• increase = septic inflammation

Lymphocytes < 15%

• increase = nonseptic inflammation

Abnormal cells found in SF differential counts

Eosinophils

LE cells

Reiter cells (vacuolated macrophages with ingested neutrophils [neutrophages])

Ragocytes (RA cells, neutrophils with small dark cytoplasmic granules with RA factor)

Lipid droplets (crush injuries)

Hemosiderin granules (pigmented villonodular synovitis)

Causes of crystals in SF

metabolic, decreased renal excretion, bone/cartilage degeneration, injection of meds into joint

What are the 2 main crystals found in SF

Primary: Monosodium urate (MSU) (Gout)

Secondary: Calcium Pyrophosphate Dehydrate (CPPD) (Pseudogout)

Causes of Gout and MSU crystals

impaired purine metabolism high purine foods, alcohol, fructose, leukemia chemo, decreased renal excretion of uric acid

Causes of Pseudogout and CPPD crystals

degenerative arthritis, elevated calcium levels

Other crystals

Hydroxyapatite = cartilage degeneration

Cholesterol = SLE, RA, notched corners

Corticosteroids = injections, flat variable plates

Calcium oxalate = renal dialysis patients

SF slide prep for crystal examination

ASAP, pH and temp will alter crystals

also seen intracellularly, WBC will degenerate

unstained or WG stain if needed

MSU crystals orientation

highly birefringent, bright against dark background, needle shaped

parallel to long axis, yellow (negative birefringence)

CPPD crystals orientation

rhombic, square, seen in neutrophil vacuoles

perpendicular along long axis, blue 9positive birefringence)

SF chemistry values similar to serum yes or no

Yes

What chemistry test is most frequently done one SF

Glucose

decrease indicates II or III arthritis

Normal SF protein value

< 3 g/dL

increased in inflammatory and hemorrhagic categories (II and IV)

SF Glucose how its obtained

after pt fasts for 8 hours

obtained at same time as blood

analyzed within 1 hour or preserved with sodium fluoride

Normal SF Glucose

<10 mg/dL lower than blood value…88 mg/dL

• 10-20 = noninflammatory

• 10-40 = inflammatory

• 20-100 or 0-80 = infection / RA

Normal SF Uric Acid

2.7-7.3

• elevated = GOUT

  • look for MSU crystals

Normal SF Lactate

<25 mg/dL

• increased in septic and bacterial arthritis >81 mg/dL

  • G(+) cocci

  • G(-) bacilli

  • N. gonorrhoeae arthritis = low or normal lactate

Enzymes found in SF

acid and alkaline phosphatase, gamma-glutamyltransferase, adenosine deaminase, muramidase, cytidine deaminase, lactate dehydrogenase, asparate aminotransferase

monitor severity and prognosis of RA

What bacteria causes Lyme disease arthritis

Borrelia burgdorferi

What bacteria causes osteoarticular tb

Mycobacterium tuberculosis

What bacteria causes venereal arthritis

Chlamydia trachomatis

N. gonorrhoeae 

Microbiology tests in SF slide

infections caused by inflammation, trauma, and systemic infections

gram stain and cultures routinely performed

culture must include chocolate agar

• Staphylococcus, Streptococcus, H. influenzae, N. gonorrhoeae

PCR available to detect microorganisms

Serological tests

majority of related tests performed on serum and fluid may only serve as a confirmation

Most common autoimmune causes of arthritis

RA and LE

Lyme disease

arthritis is frequent complication; test serum for Borrelia burgdorferi antibodies