Outcome measures and biomarkers in chronic inflammatory demyelinating polyradiculoneuropathy: from research to clinical practice

Proximity extension assay-based discovery of biomarkers for disease activity in chronic inflammatory demyelinating polyneuropathy

BACKGROUND

Objective disease activity biomarkers are lacking in chronic inflammatory demyelinating polyneuropathy (CIDP), impacting treatment decisions in clinical care and outcomes in clinical trials. Using a proximity extension assay, we aimed to identify candidate serum protein biomarkers for disease activity in CIDP.

METHOD

We collected clinical data and serum of 106 patients with CIDP. Patients starting induction treatment (n=53) and patients on maintenance treatment starting treatment withdrawal (n=40) were assessed at baseline and at 6 months (or at relapse). Patients in remission (n=13) were assessed once. Clinical disease activity was defined based on improvement or deterioration by the minimal clinically important difference on the inflammatory Rasch-built Overall Disability Scale in combination with either grip strength or the Medical Research Council sum score. Using a proximity extension assay (Olink Explore platform), 1472 protein levels were analysed in serum. Candidate proteins were selected based on fold change>0.5 or <-0.5 and p<0.05 between clinically active and inactive disease. Longitudinal changes of candidate proteins between baseline and follow-up were analysed.

RESULTS

We identified 48 candidate proteins that differed between clinically active and inactive disease on cross-sectional comparison. Five of these proteins (SUGT1, IRAK4, DCTN1, 5'-nucleotidase cytosolic IIIA (NT5C3A), glutaredoxin (GLRX)) also showed longitudinal changes consistent with disease activity changes. IRAK4 was also identified in a sensitivity analysis, using another definition for disease activity.

CONCLUSION

Our results indicate that IRAK4 and possibly SUGT1, DCTN1, NT5C3A and GLRX are candidate biomarkers for monitoring clinical disease activity in CIDP.

Validation of elevated levels of interleukin-8 in the cerebrospinal fluid, and discovery of new biomarkers in patients with GBS and CIDP using a proximity extension assay

Background

Biomarkers for diagnosis of inflammatory neuropathies, assessment of prognosis, and treatment response are lacking.

Methods

CSF and EDTA plasma from patients with Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), healthy controls (HC) and disease controls were analyzed with Olink multiplex proximity extension assay (PEA) from two independent cohorts. Levels of interleukin-8 (IL8) were further analyzed with ELISA in patients with GBS, CIDP, paraproteinemia-related demyelinating polyneuropathy (PDN), multifocal motor neuropathy (MMN), HC and disease controls. ROC analysis was performed. Outcome was measured with the GBS-disability score (GBS-ds) or Inflammatory Neuropathy Cause and Treatment (INCAT) score.

Results

In CSF, multiplex PEA analysis revealed up-regulation of IL8 in GBS compared to CIDP and HC respectively, and CIDP compared to HC. In addition, levels of IL2RA were upregulated in GBS compared to both HC and CIDP, SELE in GBS compared to HC, and ITGAM, IL6, and NRP1 in GBS compared to CIDP. In plasma, levels of MMP3, THBD and ITGAM were upregulated in CIDP compared to HC. Validation of multiplex IL8 results using ELISA, revealed increased levels of IL8 in CSF in patients with GBS and CIDP versus HC and non-inflammatory polyneuropathies (NIP) respectively, as well as in PDN versus NIP and HC. Levels of IL8 in CSF correlated with impairment in the acute phase of GBS as well as outcome at 6-months follow up.

Conclusion

IL8 in CSF is validated as a diagnostic biomarker in GBS and CIDP, and a prognostic biomarker in GBS. Multiplex PEA hereby identifies several potential biomarkers in GBS and CIDP.

Time for a standardized diagnostic response test in patients with chronic inflammatory demyelinating polyradiculoneuropathy?

Standardized pharmacological response tests are important and established diagnostic tools in the field of neurology. However, regarding therapeutic responses to intravenous immunoglobulins (IVIg) in CIDP, neither a definition of therapeutic response has been established, nor a response test has been suggested so far. Here we suggest a practical clinical approach which is supported by current literature in the field. An established standardized IVIg response test could avoid prolonged therapy without benefit for the patient and ensure a timely therapy switch or treatment escalation if required. This approach would also be advantageous due to the global scarcity of plasma derivatives as a human resource and could be the foundation to be adjusted and improved by subsequent studies.

Current clinical management of CIDP with immunoglobulins in France: An expert opinion

Treatment strategies in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) must be adapted on a case-to-case basis. Validated and reproducible tools for monitoring treatment response are required at diagnosis, when initiating treatment and throughout follow-up. A task force of French neurologists, experts in neuromuscular disease reference centers, was assembled to provide expert advice on the management of typical CIDP with intravenous immunoglobulins (Ig), and to harmonize treatment practices in public and private hospitals. The task force also referred to the practical experience of treating CIDP with Ig at the diagnostic, induction and follow-up stages, including the assessment and management of Ig dependence, and following the recommendations of the French health agency.

Disease activity in chronic inflammatory demyelinating polyneuropathy: A comparative study of clinical and skin biopsy markers

INTRODUCTION/AIMS

Epidermal nerve fiber involvement in chronic inflammatory demyelinating neuropathy (CIDP) has been reported in a limited number of patients. We quantified small-fiber involvement in a mixed cohort of patients with typical CIDP and CIDP variants to evaluate relationships with clinical outcome measures at different disease stages.

METHODS

Intraepidermal nerve fiber densities (IENFDs) were evaluated by skin punch biopsies of 23 patients with CIDP and 13 healthy controls at the forearm, thigh, and distal leg. Skin sections were optimally interpreted in all three regions in 16 CIDP patients and 10 age- and sex-matched healthy controls. Statistical analysis was performed in these subjects.

RESULTS

The IENFDs in forearm, thigh, and distal leg were similar among seven typical CIDP and nine CIDP variants. IENFDs in those regions were significantly reduced in CIDP compared with healthy controls, with a moderate negative correlation with scores on the International Neuropathy Cause and Treatment (INCAT) Upper Limb Functional Disability Scale. The reduction in IENFD compared with controls was more remarkable in the distal leg. In clinically unstable CIDP patients, the IENFDs of distal leg and forearm were significantly reduced compared with stable CIDP patients and controls. Stable CIDP patients had significantly reduced IENFDs in distal leg and forearm compared with controls.

DISCUSSION

In this exploratory study, we confirm that small fibers are also affected in CIDP. Larger studies are needed to explore longitudinal changes of IENFD in CIDP and its relation to disease stage.

Assessing deterioration using impairment and functional outcome measures in chronic inflammatory demyelinating polyneuropathy: a post-hoc analysis of the IOC trial

BACKGROUND AND AIMS

It is unclear whether frequently used cut-off values for outcome measures defining minimal clinically important differences (MCIDs) can accurately identify meaningful deterioration in chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS

We used data from the IOC trial, in which sixty clinically stable CIDP patients were randomized to IVIg withdrawal or continuation. We calculated change scores of the Inflammatory Rasch-Built Overall Disability Scale (I-RODS), grip strength, and MRC sum score (MRC-SS) and classified visits based on a treatment anchor (i.e. decision to restart/increase treatment after reaching a predefined early endpoint of deterioration). The variability of scores in patients without deterioration was calculated using the limits of agreement. We defined optimized MCIDs for deterioration and specific combinations of MCIDs from different outcome measures, and subsequently calculated the accuracies of the (combined) MCIDs.

RESULTS

Substantial variability was found in scores of the I-RODS, grip strength and MRC-SS in patients without deterioration over time, and most MCIDs were within the limits of the variability observed in patients without deterioration. Some MCID cut-offs were insensitive but highly specific for detecting deterioration, e.g. the MCID-SE of -1.96 of the I-RODS and -2 point on the MRC-SS. Others were sensitive, but less specific, e.g. -4 centiles of the I-RODS. Some combined MCIDs resulted in high specificities and moderate sensitivities.

INTERPRETATION

Our results suggest that clinically important deterioration cannot be distinguished from variability over time with currently used MCIDs on the individual level. Combinations of MCIDs might improve the accuracy of determining deterioration, but this needs validation.