AANP Family Nurse Practitioner (FNP) Certification ExamAssessmentMedium
A 48-year-old male presents with acute onset of severe pain, swelling, and redness in his left great toe. He reports consuming large amounts of alcohol and seafood the previous night. On examination, the joint is exquisitely tender, warm, and swollen. Which diagnostic finding is most definitive for confirming the suspected diagnosis?
- AElevated serum uric acid level
- BRadiograph showing joint space narrowing and erosions
- CPresence of negatively birefringent urate crystals in synovial fluid
- DNormal erythrocyte sedimentation rate (ESR)
Show answer & explanationAnswer & explanation
Correct answer: C. Presence of negatively birefringent urate crystals in synovial fluid
The patient's presentation is classic for acute gouty arthritis. While an elevated serum uric acid level is suggestive, it is not definitive (can be normal during an acute attack). The presence of negatively birefringent urate crystals in the synovial fluid, obtained via arthrocentesis, is the gold standard for confirming gout.
Why the other options are wrong
- A. Elevated serum uric acid is common in gout but can be normal during an acute attack and is not definitive for diagnosis.
- B. Radiographic changes like joint space narrowing and erosions are seen in chronic, advanced gout, not typically in an acute first episode.
- D. ESR is a non-specific inflammatory marker; a normal ESR would argue against inflammation, but it's not a diagnostic finding for gout itself.
Acute Gout Diagnosis
The definitive diagnosis of acute gouty arthritis is made by aspirating synovial fluid from the affected joint and identifying negatively birefringent, needle-shaped urate crystals under polarized light microscopy.
- Classic presentation: sudden onset, severe pain, redness, swelling of a single joint (often great toe).
- Risk factors: high purine diet, alcohol, certain medications.
- Serum uric acid can be normal during an acute attack.
Memory trick: Gout's Golden Goal: Glimpse the Crystals.