A prospective study on split-hand index as a biomarker for the diagnosis of amyotrophic lateral sclerosis

Abstract

Objective

To determine the practical diagnostic utility of split-hand index (SI) values calculated from F-wave persistence (SI_FP) and the F/M amplitude ratio (SI_F/M) for differentiating patients with amyotrophic lateral sclerosis (ALS) from other conditions. Methods: This prospective study recruited consecutive patients from Peking Union Medical College Hospital, China, between June 2019 and December 2019. Patients 18-80 years old who had clinical neuromuscular symptoms affecting the upper limbs and required electrophysiological examinations to aid diagnosis were eligible. Compound muscle action potentials (CMAPs) and F-waves recorded from the abductor pollicis brevis (APB), first dorsal interosseous muscle (FDI), and abductor digiti minimi (ADM) were examined. SI_FP and SI_F/M were calculated as: SI = (APB × FDI)/ADM. The sensitivity and specificity of SI_FP and SI_F/M in differentiating ALS from non-ALS conditions were derived using receiver operating characteristic (ROC) curves. Results: A total of 309 participants, comprising 91 (29.4%) with ALS and 218 (70.6%) with other neuromuscular disorders, were enrolled after 54 were excluded. SI_FP was significantly reduced and SI_F/M increased in the ALS group compared with the non-ALS group (p < 0.001). By ROC curve analysis, an SI_FP cutoff of 73.3 showed 85.7% sensitivity and 80.7% specificity for differentiating ALS from non-ALS. SI_F/M and SI_CMAP showed lower sensitivity (67% and 75.8%, respectively, p < 0.001) than SI_FP for ALS diagnosis. SI_FP and SI_F/M combined did not outperform SI_FP alone. Conclusion: SI_FP could be a sensitive, noninvasive neurophysiological diagnostic marker for ALS patients with affected upper limbs. In particular, an SI_FP value of 73.3 might be the optimal cutoff for diagnosing ALS.

Keywords:

• Amyotrophic lateral sclerosis
• split-hand
• split-hand index
• F-wave
• compound muscle action potential

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Acknowledgements

The authors thank all members of the Department of Neurology and electromyogram room for helping conduct this study. The authors also thank the patients and their families for their kind participation in this study.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Author contributions

ZW and LC designed the study. ZC, QD and YH collected the data. ZW and ML analyzed the data. ML interpreted the data and performed the literature search. ZW wrote the manuscript and created the figures. ML and LC edited the manuscript. LC revised the manuscript and figures.

Additional information

Funding

This work was supported by the National Key Research and Development Program of China under Grant [2016YFC0905103]; the Chinese Academy of Medical Sciences (CAMS) Innovation Fund for Medical Sciences (CIFMS) under Grant [2016-12M-1-004]; the Strategic Priority Research Program (Pilot study) ‘Biological basis of aging and therapeutic strategies’ of the Chinese Academy of Sciences under Grant [XDPB10].