Reliability and responsiveness of a graduated tuning fork in immune mediated polyneuropathies

The interobserver and intraobserver reliability of the Rydel-Seiffer (RS) g raduated tuning fork was evaluated in 113 patients with a clinically stable immune mediated polyneuropathy (83 patients who had had Guillain-Barre syn drome (GBS) in the past, 22 with a chronic inflammatory demyelinating polyn europathy (CIDP), and eight with a polyneuropathy associated with a gammopa thy of undetermined significance). Additionally, the responsiveness of this instrument was serially investigated in 20 patients with recently diagnose d GBS or CIDP and changing clinical conditions. The measures were done in t riplicate at eight different locations in the limbs and the values were com pared with the recently published vibration threshold reference values. Goo d 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 addi tion to literature findings, further evidence for incorporation of this eas ily applicable instrument in routine neurological examination.