Letter to the Editor regarding "COVID-19-Related Burden and Risk Perception in Individuals with Chronic Inflammatory Demyelinating Polyneuropathy and Multifocal Motor Neuropathy: A Cross-Sectional Study".

Dear Editor,

We read with interest the article by Musche et al. about a study of psychological distress and risk perception in 59 patients with either chronic inflammatory demyelinating polyneuropathy (CIDP) or multifocal motor neuropathy (MMN) using a survey including demographics, distress (distress thermometer), depressive symptoms (PHQ-2), anxiety (GAD-7), anxiety related to coronavirus disease 2019 (COVID-19), risk perception under immunosuppression, and frequency and type of infections since baseline [1]. It was concluded that patients with CIDP/MMN on immune medication experience reduced infection frequency, increased risk perception, increased prevalence of depression, generalized anxiety, and increased anxiety related to COVID-19 [1]. The study is attractive but raises concerns that should be discussed.

The main shortcoming of the study is that the survey was conducted online (electronically). It therefore remains uncertain how the patients’ responses were objectified. We should know how it was ensured that the patients themselves and not their carers or relatives answered the questions. Because CIDP/MMN can lead to disability, we should know how it was ensured that each of the CIDP/MMN patients was physically capable of using electronic devices.

Another shortcoming is that the study group was not homogeneous in terms of diagnostics and therapy. It is therefore hardly possible to generalize the results. The study should be repeated with either only MMN or only CIDP patients, all on the same long-term treatment.

According to the results section, only 76% of the included patients received a long-term therapy with intravenous or subcutaneous immunoglobulins (IVIG, SCIG) [1]. Therefore, the study population was not homogenous for the treatment, and it cannot be concluded that treatment had an impact on the responses given by the patients.

Because not all patients were on long-term treatment, because a number of infections are subclinical or minimally symptomatic, and because a reduced infection rate can have many other causes, it is unjustified to conclude that the immunosuppressive drugs were responsible for the reduced rate of infection. Susceptibility to infection depends on several factors, including genetics, concomitant medication, immune competence, or pre-existing conditions that compromise the immune system, which have not been considered as alternative causes.

It is not explained why patients with CIDP and MMN were selected. No mention is made of how many patients had CIDP and how many had MMN. There is no mention of how diabetes, hypertension, chronic respiratory, and cardiovascular diseases were specifically defined. Therefore, it is unclear how many CIDP/MMN patients were excluded because of any of these conditions. This figure should be specified.

The key summary point number one is not based on the study results. Because the study was limited to patients with CIDP/MMN, the results cannot be generalized to the full spectrum of immune neuropathies.

Overall, the interesting study has some limitations that call the results and their interpretation into question. Clarifying these weaknesses would strengthen the conclusions and could improve the study. To assess the impact of diagnosis and treatment on attitudes toward COVID-19, study groups of interest should be homogenized not only in terms of demographics but also in terms of diagnosis, treatment, and comorbidities. Due to the inherent disadvantages, on-site surveys should be preferred to on-line surveys. However, attempting to use an online survey also has advantages, and is timely because investigators can access a wide range of patients, including those who are unable to go to the clinic. Examining questions about psychiatric aspects of patients suffering from immune-mediated disorders in the COVID-19 era is also important. Therefore, discussion of these concerns will deepen understanding of the limitations and benefits of online surveys and the current situation of patients with immune-mediated diseases.