Testing of an Index of Pulmonary Dysfunction in Multiple Sclerosis

The reliability and validity of an Index of Pulmonary Dysfunction in Multiple Sclerosis (Index) comprised of four readily assessed clinical signs was studied. Forty patients with MS performed pulmonary function testing and underwent clinical evaluation to determine whether or not the Index correctly identified those patients with pulmonary dysfunction. The Index correctly predicted the presence or absence of significant respiratory muscle weakness (defined as Pemax less than 50% of predicted) in 32 (80%) of the subjects. All subjects who had normal expiratory muscle strength (Pemax greater than or equal to 80% of predicted) were correctly classified by the Index; however, not all patients with isolated expiratory muscle weakness were correctly identified. Test-retest reliability, interrater reliability (Spearman rho coefficients of 0.87 and 0.94, respectively), and internal consistency (alpha = .83) of the Index were acceptable. Index scores were not associated with changes in any other PFT results except residual volume, which increased with the severity of respiratory muscle weakness. The Index has acceptable validity and reliability for use in clinical practice to identify those neurological patients with expiratory muscle weakness.