What is the recommended lab workup for a 70-year-old patient presenting with numbness in the hands and feet?

Comprehensive Laboratory Workup for a 70-Year-Old with Numbness in Hands and Feet

The recommended laboratory workup for a 70-year-old patient with numbness in the hands and feet should include fasting blood glucose, hemoglobin A1c, complete blood count, vitamin B12 level, and thyroid function tests as first-line investigations. 1

Initial Assessment

• Obtain a detailed history of the numbness symptoms, including onset, progression, exacerbating factors, and associated symptoms 1
• Document any history of ulceration, amputation, vascular surgery, cigarette smoking, retinopathy, and renal disease 2
• Assess for current symptoms such as pain, burning, numbness, and vascular symptoms (leg fatigue, claudication) 2

Physical Examination

• Perform a comprehensive neurological assessment including:

  • 10-g monofilament testing (or Ipswich touch test) 2, 1
  • At least one additional sensory test: pinprick, temperature, or vibration testing with a 128-Hz tuning fork 2
  • Assessment of ankle reflexes 1, 3
  • Evaluation of position sense at the great toe 4
  • Unipedal stance test (inability to maintain for 10 seconds suggests significant neuropathy) 4

• Complete a vascular assessment including:

  • Palpation of peripheral pulses (femoral, popliteal, dorsalis pedis, posterior tibial) 2, 3
  • Assessment of capillary refill time, rubor on dependency, pallor on elevation, and venous filling time 2, 3

• Inspect the skin for integrity, deformities, ulcers, calluses, or wounds 2

Laboratory Testing

• First-line laboratory tests:

  • Fasting blood glucose and hemoglobin A1c (to assess for diabetes) 1, 5
  • Complete blood count (to evaluate for anemia) 1, 5
  • Vitamin B12 level (to assess for deficiency) 1, 5
  • Thyroid function tests (TSH, free T4) 1, 5
  • Comprehensive metabolic profile (to assess kidney and liver function) 5

• Second-line laboratory tests (if initial evaluation is inconclusive):

  • Serum protein electrophoresis with immunofixation (to evaluate for paraproteinemia) 5
  • Iron studies including ferritin (low ferritin can contribute to restless legs syndrome, which may present with similar symptoms) 6
  • HIV, hepatitis B and C testing (if risk factors present) 1

Additional Diagnostic Testing

• Ankle-Brachial Index (ABI) if peripheral arterial disease is suspected (symptoms of claudication or decreased/absent pedal pulses) 2, 1
• Exercise treadmill ABI testing if resting ABIs are normal but symptoms suggest peripheral arterial disease 1
• Toe-Brachial Index (TBI) if ABI >1.40 (indicating non-compressible arteries) 1
• Consider referral to neurology for electrodiagnostic studies (nerve conduction studies and electromyography) if initial evaluation is inconclusive 5

Common Pitfalls to Avoid

• Failing to perform a complete foot examination (should be done at least annually in patients with diabetes) 2
• Relying on a single test for diagnosing peripheral neuropathy (at least two tests should be performed) 2, 1
• Not considering non-diabetic causes of peripheral neuropathy 1
• Overlooking the need for vascular assessment in patients with neuropathic symptoms 1
• Failing to assess for fall risk in elderly patients with peripheral neuropathy 4, 7

Referrals to Consider

• Endocrinology if diabetes is diagnosed or suspected 1
• Neurology if initial evaluation is inconclusive or for additional testing (electrodiagnostic studies, specific antibody assays) 5
• Vascular surgery for significant peripheral arterial disease 1
• Podiatry for foot care and management of foot deformities, especially in patients with diabetes 2, 1