Urinalysis Chapter 12: Synovial Fluid

What is a function of synovial fluid?

Lubrication for the movable joints: diarthrosis

What nutrients does synovial fluid provide?

Nutrients for articular cartilage

How does synovial fluid affect joint compression?

It lessens shock of joint compression

What is the formation process of synovial fluid?

Ultrafiltrate of plasma across synovial membrane

What do synoviocytes secrete to make synovial fluid viscous?

Hyaluronic acid

What is a common effect of damage to articular membranes?

Pain and stiffness in the joints (arthritis)

What test is commonly performed on synovial fluid to count white blood cells?

WBC count (Hemocytometer)

What test involves examining a stained blood smear on synovial fluid?

Differential

What test is used to identify bacteria in synovial fluid?

Gram stain

What is the purpose of culturing synovial fluid?

To grow and identify microorganisms

What examination is performed to detect crystals in synovial fluid?

Crystal examination

What are the four classifications of arthritis disorders?

Noninflammatory, Inflammatory, Septic, Hemorrhagic

What is an example of a noninflammatory arthritis disorder?

Osteoarthritis

Name two types of inflammatory arthritis disorders.

Rheumatoid arthritis (RA) and systemic lupus erythematosus

What is an example of a septic arthritis disorder?

Microbial infection

What can cause hemorrhagic arthritis disorders?

Trauma, tumors, hemophilia, or other coagulation deficiencies

What is a crystal-induced inflammatory arthritis disorder?

Gout

What is another name for pseudogout?

Calcium pyrophosphate dihydrate crystal deposition disease

What is needle aspiration of a joint called?

Arthrocentesis

What is the normal amount of knee fluid?

3.5 mL

What is the knee fluid volume if it is inflamed?

>25 mL

Does normal knee fluid clot?

No, normal fluid does not clot.

What type of container should be used for microbiology specimen collection?

Sterile heparinized or SPS

What type of container should be used for hematology specimen collection?

Liquid EDTA (no powdered)

What type of container should be used for other tests?

Heparinized or non-anticoagulated

What should be done with a non-anticoagulated tube after collection?

Centrifuge and separate

What additive is used for glucose testing?

Sodium fluoride

Why should tests be performed ASAP after specimen collection?

To avoid cellular lysis and changes in crystals

What is the normal color of synovial fluid?

Clear and pale yellow (egg white)

What does a deeper yellow color in synovial fluid indicate?

Noninflammatory or inflammatory effusions; green tinge indicates infection

What color indicates a hemorrhagic or traumatic tap in synovial fluid?

Red

What is a characteristic of a traumatic tap in synovial fluid?

Uneven distribution of blood

What does milky synovial fluid indicate?

Crystal induced

What factors affect the clarity of synovial fluid?

Presence of WBCs, RBCs, synoviocytes, crystals, fat droplets, fibrin, and cellular debris

What causes turbidity in synovial fluid?

White blood cells (WBCs) or cellular debris, fibrin

What is the role of hyaluronic acid in joint movement?

It is essential for joint movement.

How does arthritis affect hyaluronic acid?

Arthritis decreases polymerization of hyaluronic acid.

What is the acceptable string length from an aspirating needle?

4 to 6 cm string is considered OK.

What is the purpose of the mucin clot test?

To assess the viscosity of synovial fluid.

What concentration of acetic acid is used in the mucin clot test?

2% to 5% acetic acid.

How are mucin clot test results reported?

Good (solid clot), fair (soft clot), low (friable clot), poor (no clot).

What is used to identify synovial fluid?

Acetic acid.

What is the most common type of cell counted in cell counts?

WBCs (White Blood Cells)

What should be done with samples for cell counts if they cannot be performed immediately?

Refrigerate or perform ASAP

What type of diluting fluid should not be used for WBC counts?

Normal WBC diluting fluid

What diluting fluids should be used for WBC counts?

Normal saline or methylene blue

What treatment may be necessary for viscous fluid before performing a WBC count?

One drop of 0.05% hyaluronidase or 37°C incubation

What device is used to perform WBC counts?

Neubauer counting chamber

What is the normal range for WBCs in a sample?

<200 WBCs/μL

What WBC count may indicate a septic condition?

>100,000 WBCs/μL

What is the first step in the counting procedure for WBCs?

Line the petri dish with moist filter paper

How much sample should be filled in the hemocytometer for counting?

10 µL

How many large squares should be counted for WBC counts less than 200 WBCs/μL?

All nine large squares

For WBC counts greater than 200 WBCs/μL, which squares should be counted?

The four corner squares

What is the procedure for performing a differential count?

Incubate with hyaluronidase, then cytocentrifuge.

What are the primary cells found in a differential count?

Monocytes, macrophages, synovial tissue cells.

What is the normal percentage of neutrophils in a differential count?

Less than 25%.

What happens to neutrophil levels in sepsis?

They increase.

What is the normal percentage of lymphocytes in a differential count?

Less than 15%.

What is indicated by a higher percentage of lymphocytes?

Non-inflammatory conditions.

How may all cells appear in a differential count?

More vacuolated.

What are LE cells?

A type of cell found in differential counts.

What are eosinophils?

A type of white blood cell found in differential counts.

What are Reiter cells?

Vacuolated macrophages with ingested neutrophils.

What are ragocytes (RA cells)?

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

What do lipid droplets indicate in a differential count?

Crush injuries.

What do hemosiderin granules indicate?

Pigmented villonodular synovitis.

What is crystal identification used for?

It is an important diagnostic test for arthritis.

Is crystal identification performed for acute, chronic, or both types of cases?

It is frequently performed for both acute and chronic cases.

What metabolic conditions can affect crystal identification?

Metabolic disorders and decreased renal function.

What are other causes that can affect crystal levels?

Increased blood levels, degeneration of bone and cartilage, and injection of corticosteroids.

What type of crystal is associated with gout?

Monosodium urate (MSU)

What type of crystal is associated with pseudogout?

Calcium pyrophosphate dihydrate (CPPD)

purple top tube

has an anticoagulant - used for cell count

What metabolic issue is linked to monosodium urate (MSU) crystals?

Impaired purine metabolism

What dietary factors can contribute to elevated levels of monosodium urate (MSU)?

High purine foods, alcohol, and fructose

What condition can lead to decreased renal excretion of uric acid?

Leukemia chemotherapy

What type of arthritis is associated with calcium pyrophosphate dihydrate (CPPD) crystals?

Degenerative arthritis

What disorders can cause elevated calcium levels leading to CPPD crystals?

Disorders causing elevated calcium levels

Why is patient history important in diagnosing crystal-related conditions?

It must be considered to understand the context of crystal formation.

What crystal is associated with cartilage degeneration and is only seen with electron microscopy?

Hydroxyapatite

What type of crystals can appear similar to urine cholesterol crystals in systemic autoimmune diseases?

Cholesterol crystals

What is a characteristic feature of cholesterol crystals?

Notched corners

What type of crystals are associated with corticosteroid injections?

Flat, variable plates

What type of crystals are commonly found in renal dialysis patients?

Calcium oxalate crystals

What are some examples of artifacts that can be mistaken for crystals?

Starch, powdered anticoagulants, dust, and scratches

What should be done with slide preparation?

Examine ASAP.

What types of crystals are seen intracellularly during slide preparation?

MSU and CPPD crystals.

What is the initial examination method for slide preparation?

Wet preparation unstained under low and high power.

What type of crystals may be seen on differential examination?

Crystals.

What shape are MSU crystals?

Needle-shaped.

Do both MSU and CPPD crystals polarize light?

Yes, both MSU and CPPD crystals polarize light.

How does MSU compare to CPPD in terms of birefringence?

MSU is highly birefringent and appears brighter than CPPD.

What method can be used to confirm the identification of MSU and CPPD crystals?

Identification can be confirmed using compensated polarized light.

What is the purpose of the red compensator in compensated polarized light?

The red compensator produces a red background and separates light into slow- and fast-moving vibrations.

How should crystals be aligned when using compensated polarized light?

Crystals should be aligned with the slow vibration.

What causes different colors to be produced in polarized light?

The linear structure of molecules causes different colors to be produced.

What is the alignment of MSU molecules under compensated light?

MSU molecules run parallel to the long axis.

What color does MSU produce under compensated light?

Yellow (negative birefringence).

What is the alignment of CPPD molecules under compensated light?

CPPD molecules run perpendicular to the long axis.