A review of clinical trial designs in amyotrophic lateral sclerosis

Split-hand index: A diagnostic and prognostic marker in amyotrophic lateral sclerosis across varying regions of onset

OBJECTIVE

The split-hand index (SI), a reliable diagnostic marker of amyotrophic lateral sclerosis (ALS), was prospectively assessed for differences across ALS subtypes and between the onset side of clinical symptoms or the dominant and contralateral sides. In addition, the prognostic utility of the SI was longitudinally assessed.

METHODS

Two hundred and forty-five ALS patients underwent measurement of SI on both sides compared with 126 neuromuscular mimic disorders (NMD). A subset of patients (N = 45) underwent longitudinal assessment of SI.

RESULTS

The SI was significantly reduced (SI _{RIGHT ALS} 5.47(4.2), SI_NMD 9.0 (5.0); P < 0.001; SI_{LEFT ALS} 5.5 (4.1), SI _NMD 9.4 (5.0), P < 0.001) on both sides in all ALS patients with prominent reduction on the onset side in upper limb onset ALS (SI _RIGHT P < 0.001; SI _LEFT P < 0.05) and in Awaji definite/probable diagnostic category (SI _RIGHT P < 0.05; SI _LEFT P < 0.05). Longitudinal studies disclosed that the rate of SI decline correlated with the decline in ALSFRS-R (r = 0.21, P < 0.05).

CONCLUSION

The SI is reduced in all ALS subtypes most prominently in upper limb onset disease, on the side of clinical onset, and in patients with Awaji definite/probable diagnostic category.

SIGNIFICANCE

The split-hand index is a reliable diagnostic and outcome biomarker across ALS subtypes and may have potential utility in a clinical trial setting, although further multicenter studies are required to confirm this.

Development and validation of a machine-learning ALS survival model lacking vital capacity (VC-Free) for use in clinical trials during the COVID-19 pandemic

Introduction: Vital capacity (VC) is routinely used for ALS clinical trial eligibility determinations, often to exclude patients unlikely to survive trial duration. However, spirometry has been limited by the COVID-19 pandemic. We developed a machine-learning survival model without the use of baseline VC and asked whether it could stratify clinical trial participants and a wider ALS clinic population. Methods. A gradient boosting machine survival model lacking baseline VC (VC-Free) was trained using the PRO-ACT ALS database and compared to a multivariable model that included VC (VCI) and a univariable baseline %VC model (UNI). Discrimination, calibration-in-the-large and calibration slope were quantified. Models were validated using 10-fold internal cross validation, the VITALITY-ALS clinical trial placebo arm and data from the Emory University tertiary care clinic. Simulations were performed using each model to estimate survival of patients predicted to have a > 50% one year survival probability. Results. The VC-Free model suffered a minor performance decline compared to the VCI model yet retained strong discrimination for stratifying ALS patients. Both models outperformed the UNI model. The proportion of excluded vs. included patients who died through one year was on average 27% vs. 6% (VCI), 31% vs. 7% (VC-Free), and 13% vs. 10% (UNI). Conclusions. The VC-Free model offers an alternative to the use of VC for eligibility determinations during the COVID-19 pandemic. The observation that the VC-Free model outperforms the use of VC in a broad ALS patient population suggests the use of prognostic strata in future, post-pandemic ALS clinical trial eligibility screening determinations.

Split-hand index for the diagnosis of amyotrophic lateral sclerosis

OBJECTIVE

Preferential wasting of the thenar group of muscles, the split hand sign, appears to be a specific feature of ALS. The present study developed a novel split-hand index (SI) and assessed its diagnostic utility in ALS.

METHODS

One hundred and seventy consecutive patients with neuromuscular symptoms (44 ALS, 126 patients with other neuromuscular disorders) were prospectively recruited according to standards for reporting of diagnostic accuracy (STARD) criteria. The SI was derived by dividing the product of the compound muscle action potential (CMAP) amplitude recorded over the first dorsal interosseous and abductor pollicis brevis by the CMAP amplitude recorded over the abductor digiti minimi.

RESULTS

The SI was significantly reduced in ALS patients (ALS 3.5 ± 0.6; patients with other neuromuscular disorders 9.1 ± 0.3, P < 0.0001), particularly in limb-onset ALS (2.3 ± 0.5, P < 0.0001). Receiver operating characteristic curve analysis indicated that SI reliably differentiated ALS from patients with other neuromuscular disorders (area under curve ALS 0.83, P < 0.0001) with an optimal SI cut-off value of 5.2 exhibiting a sensitivity of 74% and specificity 80%.

CONCLUSIONS

The split-hand index robustly differentiates ALS from mimic disorders.

SIGNIFICANCE

The split-hand index is a simple measure that could be utilized in a standard neurophysiology setting. A reduction in SI distinguishes ALS from mimic disorders, potentially facilitating an earlier diagnosis of ALS.