How is diabetic neuropathy assessed?

Assessment of Diabetic Neuropathy

All patients with type 2 diabetes should be assessed for diabetic peripheral neuropathy starting at diagnosis and all patients with type 1 diabetes should be assessed starting 5 years after diagnosis, with annual evaluations thereafter. 1

Comprehensive Assessment Approach

Clinical Evaluation

1. Small-fiber function assessment:

   • Temperature sensation testing
   • Pinprick sensation testing

2. Large-fiber function assessment:

   • Vibration perception using 128-Hz tuning fork
   • Lower-extremity reflexes (ankle reflexes)
   • 10-g monofilament testing

3. Protective sensation assessment:

   • 10-g monofilament testing (most critical for identifying feet at risk for ulceration)

The 10-g monofilament test plus at least one other neurological assessment tool is the recommended approach by the American Diabetes Association 2. This combination provides the most useful diagnostic information, with abnormal vibration perception (LR range 16-35) and abnormal monofilament testing (LR range 11-16) being highly predictive of neuropathy 3.

Diagnostic Algorithm for Distal Symmetric Polyneuropathy (DSPN)

The Chinese guidelines for diabetes care provide a useful diagnostic flowchart 1:

1. Identify if patient has diabetes
2. Check for clinical symptoms (pain, burning, tingling)
3. Perform physical examination:
   • Temperature sensation
   • Pinprick sensation
   • Vibration perception
   • Pressure sensation
   • Ankle reflexes
4. If one or more signs are positive, diagnose as DSPN
5. If signs are negative but symptoms are present, classify as possible DSPN
6. Consider neuroelectrophysiological examination when diagnosis is uncertain

Assessment for Autonomic Neuropathy

Autonomic neuropathy should be assessed in people with type 1 diabetes after 5 years of diagnosis and at diagnosis for type 2 diabetes 1. Screening includes:

1. Cardiovascular autonomic testing:

   • Heart rate variability
   • Postural hypotension testing
   • Ambulatory blood pressure monitoring

2. Gastrointestinal assessment:

   • Screening for symptoms of gastroparesis
   • Consider scintigraphy or electrogastrography if symptomatic

3. Genitourinary assessment:

   • Screening for bladder dysfunction
   • Assessment for erectile dysfunction
   • Ultrasound for bladder volume and residual urine if symptomatic

4. Other autonomic functions:

   • Skin assessment for ahidrosis, heat intolerance, dry skin
   • Evaluation for hyperhidrosis

Risk Stratification

The International Working Group on the Diabetic Foot recommends categorizing patients into four risk categories based on assessment findings 2:

• Category 0: Very low risk
• Category 1: Low risk
• Category 2: Moderate risk
• Category 3: High risk

This stratification guides the frequency of follow-up evaluations.

Common Pitfalls in Assessment

1. Failure to perform comprehensive foot examination - Relying on only one test rather than multiple complementary assessments
2. Overlooking non-diabetic causes of neuropathy - Diabetic neuropathy is a diagnosis of exclusion 1
3. Inadequate follow-up frequency - Not adjusting monitoring based on risk stratification
4. Missing asymptomatic neuropathy - Up to 50% of diabetic peripheral neuropathy may be asymptomatic 1
5. Neglecting autonomic neuropathy assessment - Focusing only on sensorimotor symptoms

Clinical Implications

Early detection of diabetic neuropathy is crucial as it allows for:

1. Implementation of preventive foot care to reduce risk of injuries, ulcers, and amputations
2. Optimization of glucose control to delay progression of neuropathy 1
3. Timely symptomatic treatment for painful neuropathy with first-line medications such as duloxetine, pregabalin, gabapentin, or amitriptyline 2, 4, 5
4. Recognition and management of autonomic neuropathy to improve symptoms and quality of life

By following a systematic approach to assessment, clinicians can identify diabetic neuropathy early and implement appropriate management strategies to reduce morbidity and mortality associated with this common complication of diabetes.