Validity and Responsiveness of Balance Measurements Using Posturography in Patients With Immune-Mediated Neuropathies

Background and Aims: Validated objective measures for balance in immune mediated neuropathies are lacking. In this study, we investigated the clinimetric properties of posturography using a force platform, a quantitative assessment of postural control. Methods: We assessed patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and IgM-related polyneuropathy (IgM-PNP) using sway parameters (path, area and amplitude) measured at multiple time points. Validity was investigated by assessing differences in sway path between patients with and without reported balance symptoms and by assessing correlations of sway path with (established) impairment measures related to balance, disability and quality of life (QoL). Responsiveness was assessed by means of an anchor-based approach, using a patient anchor and two disability scales. Results: We included 52 CIDP and 13 IgM-PNP patients. In CIDP, sway path was 25% longer in patients reporting balance symptoms relative to patients without balance symptoms (p = 0.03). There was excellent reliability between consecutive measurements in both CIDP and IgM-PNP. Moderate to good correlations were observed between sway path and an ataxia scale (CIDP: Spearman's ρ = 0.46, 95% CI: 0.2–0.69; IgM-PNP: Spearman's ρ = 0.72, 95% CI: 0.28–0.96) while correlations with related disability measures and QoL were poor. Changes in sway parameters over time were not consistently associated with changes in other outcome measures. Interpretation: Posturography measurements showed poor validity and responsiveness. Therefore, despite excellent reliability, using a force platform in clinical practice or trials for immune-mediated neuropathies cannot be recommended.