What diagnostic tests and labs should be ordered for a patient with suspected Peripheral Arterial Disease (PAD), Deep Vein Thrombosis (DVT), and statin-induced myopathy due to Rosuvastatin (rosuvastatin)?

Diagnostic Tests for Suspected PAD, DVT, and Statin-Induced Myopathy

Initial Vascular Assessment

For suspected peripheral arterial disease (PAD), deep vein thrombosis (DVT), and statin-induced myopathy, the ankle-brachial index (ABI) with pulse volume recordings (PVR) and/or Doppler waveforms should be the first diagnostic test performed. 1

For PAD Evaluation:

• Resting ABI measurement:

  • Abnormal: ABI ≤0.90
  • Borderline: ABI 0.91-0.99
  • Normal: ABI 1.00-1.40
  • Noncompressible: ABI >1.40 1

• If ABI >1.40 (noncompressible vessels): Perform toe pressure/toe-brachial index (TBI) with waveforms 1

  • Normal TBI: >0.70
  • Abnormal TBI: ≤0.70 1

• If normal or borderline resting ABI (>0.90 and ≤1.40) with exertional symptoms: Perform exercise treadmill ABI testing 1

  • A post-exercise drop in ABI below 0.90 confirms PAD 2

• For anatomical assessment if revascularization is being considered:

  • Duplex ultrasound as first-line imaging method 1
  • CTA or MRA for aorto-iliac or multisegmental/complex disease 1

For DVT Evaluation:

• Apply Wells score for clinical probability assessment: 3

  Factor	Points
  Active cancer	1
  Paralysis, paresis, or recent immobilization	1
  Bedridden ≥3 days or major surgery within 12 weeks	1
  Localized tenderness along deep veins	1
  Entire leg swollen	1
  Calf swelling ≥3 cm larger than asymptomatic side	1
  Pitting edema confined to symptomatic leg	1
  Collateral superficial veins	1
  Previous DVT	1
  Alternative diagnosis at least as likely	-2

• Diagnostic pathway:

  • High clinical probability: Proceed directly to compression ultrasonography (CUS) 3
  • Low clinical probability: D-dimer testing first, then CUS if positive 3
  • If initial CUS negative but high suspicion: Consider serial ultrasound (repeat on day 3 and day 7), or venographic-based imaging (CT venography or MR venography) 3
  • For suspected iliac vein thrombosis: Consider Doppler US of iliac veins, CT venography, or MR venography 3

For Statin-Induced Myopathy Evaluation:

• Laboratory tests:
  • Creatine kinase (CK) level to assess muscle damage
  • Liver function tests (ALT, AST)
  • Renal function tests (creatinine, BUN)
  • Thyroid function tests (hypothyroidism can increase statin myopathy risk)

Comprehensive Laboratory Assessment:

• Lipid profile: Total cholesterol, LDL-C, HDL-C, triglycerides, lipoprotein(a) 1
• Glucose metabolism: Fasting glucose, HbA1c 1
• Renal function: Creatinine, estimated GFR 1
• Complete blood count 1
• Coagulation studies: D-dimer (especially for DVT evaluation) 1, 3
• Inflammatory markers: C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) 1
• Electrolytes 1

Diagnostic Algorithm

1. Start with ABI measurement with PVR/Doppler waveforms

   • If abnormal (≤0.90): PAD confirmed, proceed with segmental pressures to determine anatomic level 1
   • If noncompressible (>1.40): Perform TBI 1
   • If normal/borderline with symptoms: Perform exercise ABI 1

2. Evaluate for DVT

   • Calculate Wells score
   • Order compression ultrasonography for high probability
   • Order D-dimer for low probability, then CUS if positive 3

3. Assess for statin-induced myopathy

   • Order CK level, liver function tests, renal function tests
   • Consider temporary statin discontinuation if CK >5x upper limit of normal with symptoms

Important Considerations

• ABI has high specificity (83-99%) but variable sensitivity (15-79%) for PAD diagnosis, with lower sensitivity in elderly patients and those with diabetes 4
• Exercise ABI testing significantly increases sensitivity for PAD detection when resting ABI is normal 2
• Ultrasound has limitations for diagnosing iliac vein thrombosis and distal DVT (below knee) 3
• D-dimer may have false-positive results in conditions like cancer, inflammation, pregnancy, or recent surgery 3
• Statin therapy is crucial for PAD patients despite myopathy concerns, as it reduces all-cause mortality by 42% and amputation risk by 35% 5

By following this systematic diagnostic approach, you can accurately diagnose PAD, DVT, and statin-induced myopathy, leading to appropriate management strategies that will improve morbidity, mortality, and quality of life outcomes.