Septic Arthritis Evaluation

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Questions and Answers

What is the primary purpose of serum uric acid in the evaluation of septic arthritis?

To rule out gout (correct)

To monitor therapeutic response

To diagnose Lyme arthritis

To determine the severity of the infection

What is the typical WBC count in synovial fluid analysis in septic arthritis?

5,000-10,000 WBC/mm3

< 10,000 WBC/mm3

10,000-50,000 WBC/mm3

> 50,000 WBC/mm3 (correct)

What is the purpose of Gram stain and aerobic and anaerobic bacterial culture in septic arthritis evaluation?

To identify the type of bacterial infection (correct)

To diagnose Lyme arthritis

To rule out gout

To monitor therapeutic response

What is the significance of PCR testing in septic arthritis evaluation?

To diagnose Lyme arthritis Signup and view all the answers

What is the primary consideration in the management of septic arthritis?

Urgent referral for treatment Signup and view all the answers

What is the approximate percentage of cases in which blood cultures are positive in septic arthritis?

25-50% Signup and view all the answers

What is the characteristic of non-inflammatory joint pain?

Typically worsens with activity Signup and view all the answers

Which of the following is a common cause of monoarticular joint pain?

Gout Signup and view all the answers

What is the characteristic of inflammatory joint pain?

Presents with redness, swelling, and warmth Signup and view all the answers

Which type of joint is commonly involved in ankylosing spondylitis?

Vertebral joints Signup and view all the answers

What is the characteristic of polyarticular joint pain?

Affects multiple joints in a symmetrical pattern Signup and view all the answers

Which of the following is a common cause of polyarticular joint pain?

Rheumatoid arthritis Signup and view all the answers

What is the importance of evaluating the number and types of joints affected in a patient's history?

To evaluate the symmetry of polyarthritis if present Signup and view all the answers

Which of the following is a common cause of oligoarticular joint pain?

Reactive arthritis Signup and view all the answers

What is the primary purpose of the 2015 ACR-EULAR Gout Classification Criteria?

To identify subjects for clinical studies Signup and view all the answers

What is the gold standard for diagnosing gout?

Joint aspiration and microscopy analysis Signup and view all the answers

What is the characteristic appearance of monosodium urate crystals under microscopy?

Needle-like appearance and strong negative birefringence Signup and view all the answers

What is the term for the condition characterized by high serum uric acid levels?

Hyperuricaemia Signup and view all the answers

What is the name of the joint commonly affected in gout flares?

First metatarsophalangeal joint Signup and view all the answers

What is the imaging modality shown in the image depicting monosodium urate crystal deposition?

Dual-energy CT Signup and view all the answers

What is the significance of periarticular erosions in radiography for the diagnosis of Rheumatoid Arthritis?

It is a characteristic finding of Rheumatoid Arthritis Signup and view all the answers

What is the minimum score required on the ACR/EULAR 2010 Diagnostic Criteria for Rheumatoid Arthritis?

6 Signup and view all the answers

What is the significance of joint involvement in the ACR/EULAR 2010 Diagnostic Criteria for Rheumatoid Arthritis?

It contributes 0-5 points to the total score Signup and view all the answers

What is the significance of acute phase reactants in the ACR/EULAR 2010 Diagnostic Criteria for Rheumatoid Arthritis?

It contributes 0-2 points to the total score Signup and view all the answers

What is the significance of duration of symptoms in the ACR/EULAR 2010 Diagnostic Criteria for Rheumatoid Arthritis?

It contributes 0-1 point to the total score Signup and view all the answers

What is the significance of serology markers in the ACR/EULAR 2010 Diagnostic Criteria for Rheumatoid Arthritis?

It contributes 0-3 points to the total score Signup and view all the answers

What is the primary purpose of complete blood count in the evaluation of septic arthritis?

To detect elevated WBC count Signup and view all the answers

What is the significance of a normal erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in septic arthritis?

It does not provide any information about the diagnosis Signup and view all the answers

What is the primary indication for imaging studies in septic arthritis?

To rule out other conditions Signup and view all the answers

What is the significance of a positive PCR test in synovial fluid analysis?

It suggests Lyme arthritis Signup and view all the answers

What is the significance of a WBC count of 50,000 WBC/mm3 in synovial fluid analysis?

It is a diagnostic criterion for septic arthritis Signup and view all the answers

What is the primary consideration in the management of septic arthritis?

Urgent referral for treatment Signup and view all the answers

What is the sensitivity of an elevated C-reactive protein (>100 mg/L) in diagnosing septic arthritis?

77% Signup and view all the answers

What is the specificity of an elevated erythrocyte sedimentation rate (>30 mm/h) in diagnosing septic arthritis?

53% Signup and view all the answers

What is the primary indication for using the 2015 ACR-EULAR Gout Classification Criteria in clinical practice?

To identify subjects who may be eligible for entry into clinical studies Signup and view all the answers

What is the characteristic appearance of monosodium urate crystals under microscopy?

Needle-like appearance with strong negative birefringence Signup and view all the answers

What is the primary role of serum uric acid levels in the evaluation of gout?

To identify hyperuricaemia Signup and view all the answers

What is the imaging modality shown in the image depicting monosodium urate crystal deposition?

Dual-energy CT Signup and view all the answers

What is the characteristic skin finding observed in patients with tophaceous gout?

Mottled hypopigmentation Signup and view all the answers

What is the gold standard for diagnosing gout?

Joint aspiration and microscopy analysis Signup and view all the answers

What is the primary purpose of joint aspiration in the evaluation of gout?

To identify the presence of monosodium urate crystals Signup and view all the answers

What is the name of the joint commonly affected in gout flares?

First metatarsophalangeal joint Signup and view all the answers

What is the characteristic of calcium pyrophosphate dihydrate crystals under birefringent microscopy?

Polymorphic, weakly positive Signup and view all the answers

What is the approximate prevalence of Rheumatoid Arthritis worldwide?

0.5-1% Signup and view all the answers

Which of the following is a genetic predisposition for Rheumatoid Arthritis?

HLA-DR1 and HLA-DR4 Signup and view all the answers

What is the typical duration of flares in calcium pyrophosphate dihydrate crystal deposition?

Days to weeks Signup and view all the answers

Which of the following is a common feature of Rheumatoid Arthritis?

Symmetrical, polyarticular pain and stiffness Signup and view all the answers

What is the percentage of osteoarthritis in people aged 65 and older?

50% Signup and view all the answers

What is a common feature of osteoarthritis in the hands?

Heberden nodes on proximal interphalangeal joints Signup and view all the answers

What is the typical morning stiffness in Rheumatoid Arthritis?

> 1 hour Signup and view all the answers

What is a characteristic of joint pain in osteoarthritis?

Worsened by movement or activity Signup and view all the answers

What is the characteristic appearance of affected joints in Rheumatoid Arthritis?

Both A and B Signup and view all the answers

What is a risk factor for developing osteoarthritis?

Family history Signup and view all the answers

What is the significance of cytokines in Rheumatoid Arthritis?

They drive chronic synovial inflammation Signup and view all the answers

What is crepitus typically felt and heard in?

Knees Signup and view all the answers

What is a common feature of osteoarthritis in the joints?

Pain on range of motion and limited range of motion Signup and view all the answers

According to the ACR/EULAR 2010 diagnostic criteria, what is the minimum score required for a diagnosis of Rheumatoid Arthritis?

6 Signup and view all the answers

What is the significance of periarticular erosions in radiography for the diagnosis of Rheumatoid Arthritis?

It is a characteristic radiographic finding Signup and view all the answers

What is the significance of serology markers in the ACR/EULAR 2010 diagnostic criteria for Rheumatoid Arthritis?

It indicates the presence of RF or ACPA Signup and view all the answers

According to the ACR/EULAR 2010 diagnostic criteria, what is the significance of joint involvement in Rheumatoid Arthritis?

It is scored based on the number and type of joints involved Signup and view all the answers

What is the significance of acute phase reactants in the ACR/EULAR 2010 diagnostic criteria for Rheumatoid Arthritis?

It indicates the presence of abnormal C-reactive protein or erythrocyte sedimentation rate Signup and view all the answers

What is the significance of duration of symptoms in the ACR/EULAR 2010 diagnostic criteria for Rheumatoid Arthritis?

It indicates the duration of symptoms as ≥ 6 weeks Signup and view all the answers

What is the first step in the transition from normouricemia to clinically evident gout?

Development of hyperuricemia Signup and view all the answers

Which of the following factors can contribute to the development of hyperuricemia?

All of the above Signup and view all the answers

What is the relationship between monosodium urate (MSU) crystal deposition and clinically evident gout?

Only some individuals with MSU crystal deposition develop clinically evident gout Signup and view all the answers

What is the clinical manifestation of gout that is characterized by the presence of tophi?

Tophaceous gout Signup and view all the answers

Which of the following is a risk factor for the development of hyperuricemia?

All of the above Signup and view all the answers

What is the relationship between hyperuricemia and clinically evident gout?

Only some individuals with hyperuricemia develop clinically evident gout Signup and view all the answers

Which of the following factors can contribute to the transition from hyperuricemia to clinically evident gout?

Multiple factors, including genetic variants, chronic kidney disease, and high body mass index (BMI) Signup and view all the answers

Which of the following is a significant complication of Rheumatoid Arthritis?

Osteoporosis Signup and view all the answers

What is the primary goal of treatment in Rheumatoid Arthritis?

To prevent irreversible joint damage Signup and view all the answers

What is the characteristic of Zain's case that increases the suspicion for Rheumatoid Arthritis?

All of the above Signup and view all the answers

What is the consequence of a 12-week delay in treatment in Rheumatoid Arthritis?

Reduced chance of achieving drug-free remission Signup and view all the answers

What is the common cause of knee pain that must be considered in Zain's case?

Osteoarthritis Signup and view all the answers

What is the significance of achieving long-term clinical remission in Rheumatoid Arthritis?

It prevents irreversible joint damage Signup and view all the answers

What is the complication of Rheumatoid Arthritis that increases the risk of coronary artery disease?

Accelerated atherosclerosis Signup and view all the answers

What is the primary purpose of the 2015 ACR-EULAR Gout Classification Criteria?

To identify subjects who may be eligible for entry into clinical studies Signup and view all the answers

What is the characteristic appearance of monosodium urate crystals under microscopy?

Needle-like appearance with strong negative birefringence Signup and view all the answers

What is the significance of dual-energy CT in the evaluation of gout?

It is used to identify monosodium urate crystal deposition in joints Signup and view all the answers

What is the characteristic skin finding observed in patients with tophaceous gout?

Mottled hypopigmentation on the dorsa of the hands Signup and view all the answers

What is the primary role of joint aspiration in the evaluation of gout?

To identify monosodium urate crystals in the synovial fluid Signup and view all the answers

What is the gold standard for diagnosing gout?

Joint aspiration and microscopy analysis Signup and view all the answers

What is the primary basis of diagnosing osteoarthritis?

Clinical diagnosis based on history and physical examination Signup and view all the answers

What is the term for the condition characterized by high serum uric acid levels?

Hyperuricaemia Signup and view all the answers

What is the name of the joint commonly affected in gout flares?

First metatarsophalangeal joint Signup and view all the answers

When is X-ray imaging typically used in the evaluation of osteoarthritis?

When diagnosis is in doubt or strong suspicion for other etiology Signup and view all the answers

What is the primary role of CT or MRI in the evaluation of osteoarthritis?

To rule out other conditions or when diagnosis is in doubt Signup and view all the answers

What is the primary indication for ultrasonography in the evaluation of osteoarthritis?

To rule out other conditions or when diagnosis is in doubt Signup and view all the answers

What is the characteristic radiographic finding in osteoarthritis?

All of the above Signup and view all the answers

What is the primary role of laboratory testing in the evaluation of osteoarthritis?

Not usually required Signup and view all the answers

What is the typical feature of joint destruction in osteoarthritis?

Erosion of the joint Signup and view all the answers

What is the primary indication for referral for joint replacement in osteoarthritis?

When imaging studies show advanced disease Signup and view all the answers

Study Notes

Septic Arthritis – Evaluation

Complete blood count: elevated WBC count
Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP): can be normal, used to monitor therapeutic response when elevated
Serum uric acid: should not be elevated, used to rule out gout
Blood cultures: positive in 25-50% of cases

Septic Arthritis – Arthrocentesis

Synovial fluid analysis: WBC count > 50,000 WBC/mm3, differential >90% polymorphonuclear cells
Gram stain, aerobic and anaerobic bacterial culture
Borrelia burgdorferi cannot be cultured from synovial fluid; PCR testing if suspecting Lyme arthritis (positive in 85% of patients)

Septic Arthritis – Imaging

X-ray, ultrasonography, MRI may be considered

Septic Arthritis – Management

Medical emergency: needs immediate diagnosis and urgent referral for treatment
Types of joints involved: vertebral, sacroiliac, wrists, carpometacarpals, MCP, PIP, DIP, ankle, MTP, shoulders, elbows, hips, knees

Inflammatory Joint Pain vs. Non-Inflammatory Joint Pain

Inflammatory joint pain: characterized by redness, swelling, warmth, tenderness, morning stiffness, and worsens with inactivity
Causes: infection, gout, rheumatoid arthritis, calcium pyrophosphate deposition disease, juvenile RA, systemic lupus erythematosus
Non-inflammatory joint pain: may or may not present with swelling and tenderness, but other signs are absent; worsens with activity
Causes: osteoarthritis, trauma, polymyalgia rheumatica, sarcoidosis, spondyloarthritides, reactive arthritis, psoriatic arthritis, ankylosing spondylitis, enteropathic arthritis

History

Evaluate number and types of joints affected and symmetry if polyarthritis is present
Onset: sudden vs. gradual

Gout – Evaluation

Based on clinical diagnosis, classification criteria, and microscopy-based diagnosis of synovial fluid
2015 ACR-EULAR Gout Classification Criteria: not meant for diagnosis, but can help inform the clinician; intended for research purposes
Serum uric acid levels: identify hyperuricaemia
Gold standard for diagnosis: joint aspiration and microscopy analysis showing presence of monosodium urate crystals

Rheumatoid Arthritis (RA) – Evaluation

Classification criteria: ACR/EULAR 2010 criteria replaced the 1987 ARA criteria
Lab findings:
- Radiography: periarticular erosions, osteopenia, joint space narrowing
- Inflammatory markers: ESR, CRP
- Serology markers: RF, ACPA, or both
Seropositive RA: 75-85% will test positive for RF, ACPA, or both

ACR/EULAR 2010 Diagnostic Criteria for RA

At least 1 joint with definite clinical synovitis (swelling) not explained by another disease plus 1 of the following:
- Presence of long-standing disease previously satisfying classification criteria
- Presence of ≥ 2 typical periarticular erosions
- Score ≥ 6 on the following criteria:
  - Joint involvement (0-5)
  - Serology (0-3)
  - Acute phase reactants (0-2)
  - Duration of symptoms (0-1)

Septic Arthritis – Evaluation

Complete blood count: elevated WBC count
Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP): can be normal, but when elevated, used to monitor therapeutic response
Serum uric acid: should not be elevated, used to rule out gout
Blood cultures: positive in 25-50% of cases
Arthrocentesis for synovial fluid analysis: WBC count > 50,000 WBC/mm3, synovial fluid WBC differential > 90% polymorphonuclear cells
Gram stain, aerobic and anaerobic bacterial culture
Borrelia burgdorferi cannot be cultured from synovial fluid, PCR testing if suspecting Lyme arthritis (positive in 85% of patients)
Imaging may be considered: X-ray, ultrasonography, MRI

Septic Arthritis – Management

Medical emergency: needs immediate diagnosis and urgent referral for treatment
Physical Exam:
- Fever: sensitivity 46%, specificity 31%
- Serum laboratory values:
  - Abnormal peripheral WBC count (>10,000/µL): sensitivity 90%, specificity 36%
  - Elevated erythrocyte sedimentation rate (>30 mm/h): sensitivity 95%, specificity 29%
  - Elevated C-reactive protein (>100 mg/L): sensitivity 77%, specificity 53%

Gout – Evaluation

Based on clinical diagnosis, classification criteria, and microscopy-based diagnosis of synovial fluid
2015 ACR-EULAR Gout Classification Criteria: not meant for diagnosis, but can help inform the clinician; intended for research purposes
Serum uric acid levels: to identify hyperuricaemia
Gold standard for diagnosis: joint aspiration and microscopy analysis showing presence of monosodium urate crystals
Other tests: ultrasonography, dual-energy CT

Calcium Pyrophosphate Dihydrate Crystal Deposition (Pseudogout)

Aka pseudogout
Persons > 65 years old
Onset: sudden
Duration: flares lasting days to weeks
Morning pain or stiffness usually present
Calcium pyrophosphate dihydrate crystals: polymorphic, weakly positive under birefringent microscopy

Rheumatoid Arthritis (RA)

0.5-1% worldwide prevalence
Higher risk in women (2-3x higher than men), smokers, patients with family history of RA
Genetic predisposition: HLA-DR1 and HLA-DR4
Systemic autoimmune inflammatory disease
Chronic/relapsing destructive synovitis: local inflammation, cartilage destruction, bone erosion
Cytokines (TNF-α, IL-1, IL-6) drive chronic synovial inflammation

Rheumatoid Arthritis (RA) - Clinical Features

Symmetrical, polyarticular pain and stiffness: most often affecting wrists, PIP, MCP, MTP joints
Morning stiffness > 1 hour
Systemic symptoms: fatigue, weight loss, anemia
Visible boggy swelling caused by synovitis
Palpable synovial thickening
Affected joint painful if pressure applied on palpation or with movement
Advanced disease: ulnar deviation, MCP joint subluxation, swan neck deformity, Boutonniere deformity
Extra-articular manifestations: accelerated atherosclerosis, pericarditis, keratoconjunctivitis sicca, episcleritis/scleritis, interstitial lung disease, pulmonary nodules, rheumatoid nodules, pleural effusion, vasculitis

Osteoarthritis

Prevalence increases with age: 7.3% in ages 18-44; 30% in ages 45-64; 50% in ages 65 and older
Women > men
Other risk factors: overweight/obese, previous joint injury, family history, frequent bending/squatting, repetitive impact
Degenerative disorder of articular cartilage associated with hypertrophic bone changes
Onset: gradual
Duration: lifelong with flares
Usually no morning pain or stiffness (or short-lived)

Osteoarthritis – Clinical Features

Asymmetric joint pain and stiffness: commonly affecting hands, knees, hips, feet, spine
Joint pain worsened by movement/activity, especially following a period of rest
Joint swelling and tenderness
Bony enlargement in prolonged or severe OA
Pain on range of motion and limitation of range of motion
Crepitus (typically knee) may be felt and heard
Bouchard nodes on proximal interphalangeal joint
Heberden nodes on distal interphalangeal joints

Gout

Gout occurs in several stages: hyperuricaemia, monosodium urate (MSU) crystal deposition, and clinical manifestations (gout flares, chronic gouty arthritis, and tophaceous gout)
Factors contributing to the transition from hyperuricaemia to clinically evident gout are not well understood
Hyperuricaemia can be caused by genetic variants, chronic kidney disease, high body mass index (BMI), medications, and dietary factors

Diagnosis of Gout

Based on clinical diagnosis, classification criteria, and microscopy-based diagnosis of synovial fluid
2015 ACR-EULAR Gout Classification Criteria not meant for diagnosis, but can help inform the clinician; intended for research purposes
Serum uric acid levels to identify hyperuricaemia
Joint aspiration and microscopy analysis showing the presence of monosodium urate crystals (identified by needle-like appearance and strong negative birefringence) is the gold standard for diagnosis
Other tests: ultrasonography, dual-energy CT

Rheumatoid Arthritis (RA)

Classification criteria: ACR/EULAR 2010 criteria replaced the 1987 ARA criteria
Lab findings: radiography (periarticular erosions, osteopenia, joint space narrowing), inflammatory markers (ESR, CRP), serology markers (Rheumatoid factor, Anti-citrullinated protein antibodies (ACPA))
ACR/EULAR 2010 Diagnostic Criteria for RA: at least 1 joint with definite clinical synovitis plus 1 of the following:
- Presence of long-standing disease previously satisfying classification criteria
- Presence of ≥ 2 typical periarticular erosions
- Score ≥ 6 on the following criteria:
  - Joint involvement (0-5)
  - Serology (0-3)
  - Acute phase reactants (0-2)
  - Duration of symptoms (0-1)

Management of RA

Low threshold for referral to rheumatologist
Goals of treatment:
- Early diagnosis and early initiation of treatment to prevent irreversible joint damage
- Achieve long-term clinical remission
- Optimize quality of life
- Monitor for extra-articular complications
Complications of RA:
- Osteopenia and osteoporosis → fracture
- Lung manifestations
- Accelerated atherosclerosis → coronary artery disease, peripheral vascular disease
- Increased insulin resistance, diabetes mellitus
- Vasculitis, thromboembolic disease
- Depression
- Anemia of chronic disease
- Felty syndrome (RA, splenomegaly, neutropenia)

Osteoarthritis

Primarily a clinical diagnosis based on history and physical examination
Imaging not required in patients with risk factors and typical symptoms
X-ray can confirm diagnosis and rule out other conditions; helpful before referral for joint replacement
May see joint space narrowing, osteophyte formation, subchondral sclerosis, and joint destruction on X-ray
CT or MRI when diagnosis is in doubt or strong suspicion for other etiology
Laboratory testing not usually required

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Description

This quiz covers the evaluation of septic arthritis, including complete blood count, ESR, CRP, serum uric acid, and arthrocentesis for synovial fluid analysis.