Evaluation of Relationship Between Laboratory, Electrodiagnostic, and Functional Parameters in Patients With Amyotrophic Lateral Sclerosis; A Cross Sectional Study

Amyotrophic lateral sclerosis (ALS) is an adult-onset motor neuron disease with a poor prognosis that leads to limb and or bulbar muscle degeneration. Several demographic and biological factors have prognostic importance, but little data exist on the relationship between clinical, electrodiagnostic, and laboratory markers as predictors of disease progression. We aimed to assess the relationships between different aspects of ALS patients’ clinical, electrodiagnostic, and laboratory features and their level of functioning. 

We included 27 ALS patients diagnosed within the last two years. A neurology resident conducted clinical assessment and electrodiagnostic studies. The motor unit number index (MUNIX) and compound motor action potential (CMAP) were used to measure motor unit loss. Serum creatinine, urea, albumin, and creatine kinase were measured as laboratory markers. We used the Persian version of the ALS functional rating scale (ALS-FRS) as the main outcome measure. The Pearson correlation coefficient was calculated to assess the correlations using the SPSS software, version 16.

None of the demographic or laboratory parameters were correlated with ALS-FRS. Patients with the onset of disease in the limbs had a higher MUNIX score than those with bulbar onset. Also, increased body mass index (BMI) was associated with lower CMAP and MUNIX scores (P=0.02). Higher serum creatinine levels were significantly associated with higher lower limb MUNIX (P=0.04). Higher lower limb MUNIX was associated with a higher lower limb functional score. 

Decreased serum creatinine may indicate lower limb motor unit loss in patients with ALS. Also, MUNIX scores may be used as substitutes for ALS-FRS in ALS trials. Further research is needed to elucidate the clinical application of these findings.