Synovial Fluid Analysis

Synonym/Acronym

Arthrocentesis, joint fluid analysis, knee fluid analysis.

Rationale

To identify the presence and assist in the management of joint disease related to disorders such as arthritis and gout.

Patient Preparation

Refer to the study titled “Arthroscopy” for additional and detailed information regarding patient preparation. Note that there are no fluid restrictions unless by medical direction. Fasting for at least 12 hr before the procedure is recommended if fluid glucose measurements are included in the analysis. The patient may be asked to be NPO after midnight.

Regarding the patient’s risk for bleeding, the patient should be instructed to avoid taking natural products and medications with known anticoagulant, antiplatelet, or thrombolytic properties or to reduce dosage, as ordered, prior to the procedure. Number of days to withhold medication is dependent on the type of anticoagulant. Note the last time and dose of medication taken. Protocols may vary among facilities.

Normal Findings

Method: Macroscopic evaluation of appearance; spectrophotometry for glucose, lactic acid, protein, and uric acid; Gram stain, acid-fast stain, and culture for microbiology; microscopic examination of fluid for cell count and evaluation of crystals; ion-selective electrode for pH; nephelometry for RF and C3 complement; indirect fluorescence for ANAs.

Test		Normal Result
Color		Colorless to pale yellow
Clarity		Clear
Viscosity		High
ANA		Parallels serum level
C3		Parallels serum level
Glucose		Less than 10 mg/dL of blood level
Lactic acid		5–20 mg/dL
pH		7.2–7.4
Protein		Less than 3 g/dL
RF		Parallels serum level
Uric acid		Parallels serum level
Crystals		None present
RBC count		None
WBC count		Less than 200 cells/microL
Neutrophils		Less than 25%
WBC morphology		No abnormal cells or inclusions
Gram stain and culture		No organisms present
AFB smear and culture		No AFB present

AFB = acid-fast bacilli; ANA = antinuclear antibodies; C3 = complement; RBC = red blood cell; RF = rheumatoid factor; WBC = white blood cell.

Critical Findings and Potential Interventions ⬆ ⬇

Positive culture findings in any sterile body fluid.
Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.

Overview ⬆ ⬇

Study type: Body fluid; Synovial fluid collected in a red-top tube for antinuclear antibodies [ANAs], complement, crystal examination, protein, rheumatoid factor [RF], and uric acid; sterile [red-top] tube for microbiological testing; lavender-top [EDTA] tube for mucin clot/viscosity, complete blood count [CBC] and differential; gray-top [sodium fluoride (NaFl)] tube for glucose; green-top [heparin] tube for lactic acid and pH; related body system: Immune and Musculoskeletal systems.

Synovial fluid analysis is performed via arthrocentesis, an invasive procedure involving insertion of a needle into the joint space. Synovial effusions are associated with disorders or injuries involving the joints. The most commonly aspirated joint is the knee, although samples also can be obtained from the shoulder, hip, elbow, wrist, and ankle if clinically indicated. Joint disorders can be classified into five categories: noninflammatory, inflammatory, septic, crystal-induced, and hemorrhagic. The mucin clot test is used to correlate the qualitative assessment of synovial fluid viscosity with the presence of hyaluronic acid. The test is performed by mixing equal amounts of synovial fluid and 5% acetic acid solution on a glass slide and grading the ropiness of the subsequent clot as good, fair, or poor. Long, ropy strands are seen in normal synovial fluid.

Indications ⬆ ⬇

Administration of anti-inflammatory medications by injection.
Assist in the diagnosis of arthritis.
Assist in the evaluation of joint effusions.
Assist in the diagnosis of joint infection.
Differentiate gout from pseudogout.

Interfering Factors ⬆ ⬇

Blood in the sample from traumatic arthrocentesis may falsely elevate the RBC count.
Undetected hypoglycemia or hyperglycemia may produce misleading glucose values.
Refrigeration of the sample may result in an increase in monosodium urate crystals secondary to decreased solubility of uric acid; exposure of the sample to room air with a resultant loss of carbon dioxide and rise in pH encourages the formation of calcium pyrophosphate crystals.

Potential Medical Diagnosis: Clinical Significance of Results ⬆ ⬇

Fluid Values Increased In

Acute bacterial infection: Elevated WBC count with marked predominance of neutrophils (greater than 90% neutrophils), positive Gram stain, positive cultures, possible presence of rice bodies, increased lactic acid (produced by bacteria), and complement levels paralleling those found in serum (may be elevated or decreased)
Gout: Elevated WBC count with a predominance of neutrophils (90% neutrophils), presence of monosodium urate crystals, increased uric acid, and complement levels paralleling those of serum (may be elevated or decreased)
Osteoarthritis, traumatic arthritis, degenerative joint disease: Elevated WBC count with less than 25% neutrophils and the presence of cartilage cells
Pseudogout: Presence of calcium pyrophosphate crystals
Rheumatoid arthritis: Elevated WBC count with a predominance of neutrophils (greater than 70% neutrophils), presence of ragocyte cells and possibly rice bodies, presence of cholesterol crystals if effusion is chronic, increased protein, increased lactic acid, and presence of rheumatoid factor
Systemic lupus erythematosus (SLE): Elevated WBC count with a predominance of neutrophils, presence of SLE cells, and presence of antinuclear antibodies
Trauma, joint tumors, or hemophilic arthritis: Elevated RBC count, increased protein level, and presence of fat droplets (if trauma involved)
Tuberculous arthritis: Elevated WBC count with a predominance of neutrophils (up to 90% neutrophils), possible presence of rice bodies, presence of cholesterol crystals if effusion is chronic, in some cases a positive culture and smear for acid-fast bacilli (results frequently negative), and lactic acid

Fluid Values Decreased in (Analytes in Parentheses Are Decreased)

Acute bacterial arthritis (glucose and pH)
Gout (glucose)
Rheumatoid arthritis (glucose, pH, and complement)
SLE (glucose, pH, and complement)
Tuberculous arthritis (glucose and pH)

Nursing Implications, Nursing Process, Clinical Judgement ⬆

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

Discuss how this procedure can assist in assessing joint health.
Explain that a synovial fluid sample is needed for the test.
Explain that the procedure takes 20 min to complete and may be performed in a medical office.
Review the procedure with the patient. Refer to the study titled “Arthroscopy” for additional detailed information pertaining to patient preparation and specimen collection procedure.
Advise that discomfort experienced with the needle insertion will be minimized with local anesthetics and systemic analgesics; the anesthetic injection may cause an initial stinging sensation.
Explain that a sedative and/or analgesia will be administered to promote relaxation and reduce discomfort prior to needle insertion through the joint space.
Explain that it may be necessary to remove hair from the site before the procedure.

Procedural Information

Positioning for this procedure is in a comfortable sitting or supine position.
The site is cleansed with antiseptic solution and draped with sterile towels.
The skin is anesthetized and a large needle is inserted through the joint space; a “popping” sensation may be experienced as the needle penetrates the joint.
A syringe is used to remove fluid at the collection site.
Manual pressure may be applied to facilitate fluid removal.
Gentle pressure is used to inject ordered medication into the joint after sample collection.
When the procedure is completed, the needle is withdrawn and direct pressure applied to the site for a few minutes. If there is no evidence of bleeding, a sterile dressing is applied to the site and an elastic bandage to the joint.
Samples are placed in properly labeled specimen containers and promptly transported to the laboratory for processing and analysis. If bacterial culture and sensitivity tests are to be performed, any antibiotic therapy being received should be recorded on the specimen label.

Potential Nursing Actions

Make sure a written and informed consent has been signed prior to the procedure and before administering any medications.

After the Study: Implementation & Evaluation Potential Nursing Actions

Avoiding Complications

Monitor the patient for complications related to the procedure.
Explain the importance of immediately reporting elevated temperature, excessive pain, bleeding, swelling, or inability to move the joint.
Observe/assess puncture site for bleeding, bruising, inflammation, and excessive drainage of synovial fluid approximately every 4 hr for 24 hr and daily thereafter for several days.

Treatment Considerations

Follow postprocedure vital sign and assessment protocol.
Resume the usual diet and medications, as directed by the HCP.
Monitor for pain and nausea. Administer ordered antiemetic and analgesic medications as needed.
Explain the importance of applying an ice pack to the site for 24 to 48 hr.
Administer ordered antibiotics and instruct the patient in the importance of completing the entire course of antibiotic therapy even if no symptoms are present.
Be supportive of impaired activity related to anticipated chronic pain resulting from joint inflammation, impairment in mobility, musculoskeletal deformity, and loss of independence.

Clinical Judgement

Consider which ancillary will be most beneficial toward supporting changed physical ability.

Follow-Up and Desired Outcomes

Acknowledges contact information provided for the American College of Rheumatology (www.rheumatology.org) or Arthritis Foundation (www.arthritis.org).