Synovial Fluid Flashcards
What is synovial fluid?
Joint fluid formed by synovial cells lining the joint and by ultrafiltration of plasma.
What does the synovial membrane do?
Acts like the blood-brain barrier; higher molecular weight compounds can’t cross.
What is hyaluronate?
A mucoprotein containing hyaluronic acid found only in synovial fluid, providing lubrication, nutrients, and viscosity.
Why examine joint fluid?
To assess swelling of the joint.
What are normal joint fluid levels?
0.1-2 mL of fluid; amount taken depends on swelling.
What is arthrocentesis?
The procedure of removing joint fluid.
What should normal joint fluid look like?
Clear to pale yellow, viscous, should not be clotted, and contain no blood.
How should collected joint fluid be processed?
It should go in 3 separate tubes: EDTA tube for cell counts, Heparin/non-additive tube for chemistry/serology, and a non-additive tube for microbiology.
What are the parameters of non-inflammatory joint fluid?
Clear fluid, normal viscosity, WBC <1,000/mL, glucose equal to serum glucose, neutrophils <30%.
What are the parameters of inflammatory joint fluid?
Less viscous, slightly cloudy appearance, high WBC count, more than 50% neutrophils, decreased glucose compared to serum glucose, presence of crystals.
What are the parameters of septic joint fluid?
Cloudy, yellowish/greenish, WBC count >100,000/mL, 75-80% neutrophils, decreased glucose.
What are the parameters of hemorrhagic joint fluid?
Red color, lower viscosity, more RBCs than WBCs, glucose levels normal to decreased.
What is the String Test?
A screening test where fluid should form a string 4-6 cm long before dropping from the pipette tip.
What is the Mucin Clot Test?
A test where hyaluronate and acetic acid form a clot; qualitative and quantitative assessments can be made.
use 2-5% acetic acid
What should be added before doing a cell count?
Hyaluronidase, an enzyme that breaks down hyaluronate.
What should you not add to destroy RBCs?
Glacial acetic acid, as it will cause clotting; hypotonic saline should be used instead.
What is an LE cell?
A macrophage that ingests neutrophils, present in 90% of people with active lupus.
LE= lupus erythematosus
What is the first crystal to look for in synovial fluid?
Monosodium urate (uric acid) crystals, seen in gout; characterized by needle-like projections and negative birefringence.
What are calcium pyrophosphate crystals associated with?
Increased levels of calcium deposits; associated with pseudo gout and degenerative arthritis.
affects larger joints
rhombus shapes
POSITIVE bifringence
What do corticosteroid crystals indicate?
Presence in patients on steroids, such as those with lupus or rheumatoid arthritis.
POSITIVE AND NEGATIVE BIREFRINGENCE
What do cholesterol crystals look like?
Rectangles with notched corners, seen in lipidemia and chronic RA; does not stain.
What should glucose levels in synovial fluid be?
They should be similar to serum values, not differing more than 10%.
What is the Rheumatoid Factor?
An IgM produced against the altered Fc portion of IgG, found in 90% of active rheumatoid arthritis cases.
found in rheumatoid arthritis
What complement levels should be looked for in synovial fluid?
C3 and C4 levels; total complement levels decrease when active.
levels decrease because being spilt and utilized
What should be looked for in microbiology testing of synovial fluid?
Septic arthritis causes, such as Neisseria Gonorrhea, MRSA, and Borrelia antibodies.
What are synovial lining cells?
Cells seen in synovial fluid that are larger than lymphocytes.
hyaluronate purpose
lubrication, nutrients, and viscosity
how does synovial fluid become hemorrhagic?
bleeding in joints due to malignancy, sickle cell anemia, traumatic injury, coagulation deficiencies
what does hematology do for synovial fluid?
look macroscopically
look at viscosity
cell count
for the mucin clot test what is the qualitative part
joint fluid and add a drop or 2 of acetic acid and shake for 5-10 sec
let it sit for it to clot
normal= solid clot
less = half a clot
severely decreased= no clot
why can’t you add glacial acetic acid to destroy RBCs
it will clot because acetic acid
ADD: hypotonic saline
what are ID crystals for
help identify different disease states
look in brightfield microscope and confirm in a polarizing microscope
ID needs to be done within a few hours within collection or will break down
what crystal is put under polarizing microscope and see maltese cross formation
cholesterol crystals
as complement levels go back to normal this indicates
inflammatory conditions are in check
what else is looked for in the micro section for synovial fluid
antibodies to Borrelia
-agent of Lyme disease
-sign of this is joint pain
