Evaluation of scales and measurement instruments in immune-mediated polyneuropathies

Immune-mediated neuropathies mainly include Guillain-Barre syndrome (GBS) (most common form: acute inflammatory demyelinating polyneuropathy (AJDP)), chronic inflammatory demyelinating polyneuropathy (CIDP), neuropathy associated with monoclonal gammopathy of undetermined significance (MGUSP), and multifocal motor neuropathy (MMN) (1-11). Electrophysiological examination in these patients generally reveals features of a demyelinating polyneuropathy. These neuropathies have become increasingly important in clinical neurology because they are readily diagnosable and potentially treatable. Evidence has emerged from many papers in the last decade to indicate that these illnesses represent part of a continuum separated by their neuromuscular dysfunction pattern, time course and response to various treatments (Figure I; 1-11). However, the distinction between these illnesses is in some aspect somewhat artificial. In the following, selected aspects of these diseases are discussed with particular emphasis on clinical presentation and outcome measures applied in clinical studies published from January 1988 to January 1999 that included patients with one of these disorders

The Rasch-built Pompe-specific activity (R-PAct) scale.

We constructed a patient-based interval scale using Rasch analysis, specifically suited to quantify the effects of Pompe disease on patient's ability to carry out daily life activities and their social participation: Rasch-built Pompe-specific Activity scale. Between July 2005 and April 2011, 186 patients aged 16 or older, participated to develop this scale. External construct validity was determined through correlations with the MRC sumscore and Rotterdam Handicap Scale. Furthermore, test-retest reliability was determined in a subgroup of 44 patients. Finally, individual person-level responsiveness was used to determine the proportion of patients demonstrating significant improvement or deterioration during their natural disease course, or during treatment with enzyme replacement therapy. Of the original 49 items, 31 were removed after investigation of model fit, internal reliability, threshold examination, item bias, and local dependency. The remaining 18 items were ordered on a linearly weighted scale and demonstrated good discriminative ability (Person Separation Index 0.96), external construct validity (intraclass correlation coefficient (ICC) for MRC sumscore 0.82, and for the Rotterdam handicap scale 0.86), reliability of person's location (ability comparison: ICC 0.95), and responsiveness. We therefore conclude that the R-PAct scale enables us to accurately detect limitations in activities and social participation throughout the entire disease spectrum in patients with Pompe disease. Copyrigh

Reliability and responsiveness of a graduated tuning fork in immune mediated polyneuropathies. The Inflammatory Neuropathy Cause and Treatment (INCAT) Group

The interobserver and intraobserver reliability of the Rydel-Seiffer (RS) graduated tuning fork was evaluated in 113 patients with a clinically stable immune mediated polyneuropathy (83 patients who had had Guillain-Barre syndrome (GBS) in the past, 22 with a chronic inflammatory demyelinating polyneuropathy (CIDP), and eight with a polyneuropathy associated with a gammopathy of undetermined significance). Additionally, the responsiveness of this instrument was serially investigated in 20 patients with recently diagnosed GBS or CIDP and changing clinical conditions. The measures were done in triplicate at eight different locations in the limbs and the values were compared with the recently published vibration threshold reference values. Good interobserver and intraobserver agreements (quadratic weighted kappa=0.67-0.98) and high responsiveness values (standardised response mean scores>0.8) were demonstrated for the RS tuning fork. These results provide, in addition to literature findings, further evidence for incorporation of this easily applicable instrument in routine neurological examination