The Sensitivity and Specificity of Split-Hand Index Using Muscle Sonography

Area of Science:

• Neurology
• Diagnostic Imaging
• Musculoskeletal Ultrasound

Background:

• The split-hand index (SHI) is a potential diagnostic marker for amyotrophic lateral sclerosis (ALS).
• Muscle ultrasound (MUS) offers a non-invasive method for assessing SHI.
• The diagnostic specificity of sonographic SHI for motor neuron diseases requires further investigation.

Purpose of the Study:

• To evaluate the specificity of the split-hand index (SHI) derived from muscle ultrasound (MUS) in diagnosing amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA).
• To compare the diagnostic accuracy of sonographic SHI in differentiating between ALS, SMA, polyneuropathy, myopathy, and healthy controls.

Main Methods:

• Quantitative sonographic evaluation of muscle thickness in abductor pollicis brevis (APB), first dorsal interosseous (FDI), and abductor digiti minimi (ADM) muscles.
• Recruitment of 181 patients with ALS, SMA, polyneuropathy, or myopathy, and 65 healthy controls.
• Calculation of the split-hand index (SHI) and determination of area under the curve (AUC), sensitivity, and specificity for group differentiation.

Main Results:

• Sonographic SHI demonstrated good to excellent accuracy (AUC 0.83-0.92) in differentiating patient subgroups from healthy controls.
• Diagnostic accuracy was poorer when differentiating between different patient subgroups (AUC 0.54-0.74).

Conclusions:

• Muscle ultrasound-derived SHI is valuable for distinguishing neurological patients from healthy individuals.
• The specificity of sonographic SHI for diagnosing specific motor neuron diseases, such as ALS and SMA, is limited.
• Further research is needed to refine the diagnostic utility of SHI in differentiating between various neuromuscular disorders.