• Susana Pinto and Mamede de Carvalho.
• a Instituto de Medicina Molecular and Institute of Physiology, Faculty of Medicine , University of Lisbon , Portugal and.
• Amyotroph Lateral Scler Frontotemporal Degener. 2017 Feb 1; 18 (1-2): 86-91.

IntroductionSlow vital capacity (SVC) and forced vital capacity (FVC) are the most frequent used tests evaluating respiratory function in amyotrophic lateral sclerosis (ALS). No previous study has determined their interchangeability.ObjectiveTo evaluate SVC-FVC correlation in ALS.MethodsConsecutive definite/probable ALS and primary lateral sclerosis (PLS) patients (2000-2014) in whom respiratory tests were performed at baseline/4-6months later were included. All were evaluated with revised ALS functional rating scale, the ALSFRS respiratory (R-subscore) and bulbar subscores, SVC, FVC, maximal inspiratory (MIP) and expiratory (MEP) pressures. SVC-FVC correlation was analysed by Pearson product-moment correlation test. Paired t-test compared baseline/follow-up values. Multilinear regression analysis modelled the relationship between tested variables.ResultsWe included 592 ALS (332 men, mean onset age 62.6 ± 11.8 years, mean disease duration 15.4 ± 15 months) and 19 PLS (11 men, median age 54 years, median disease duration 5.5 years) patients. SVC and FVC predicted values decreased 2.15%/month and 2.08%/month, respectively. FVC and SVC were strongly correlated. Both were strongly correlated with MIP and MEP and moderately correlated with R-subscore for the all population and spinal-onset patients, but weakly correlated for bulbar-onset patients.ConclusionsFVC and SVC were strongly correlated and declined similarly. This correlation was preserved in bulbar-onset ALS and in spastic PLS patients.

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