79 protocol for QST procedures, recommends the MLi. In contrast, the Besta criteria, the most widely recognized and standardized diagnostic criteria for SFN, recommends the MLe.7 Known disadvantages of the MLe are high time consumption and desensitization14 because of numerous repeated measurements. The selection of TTT parameters and measuring sites has not been standardized yet. For example measuring TTT at both feet was suggested by one group6 while another group measured TTT at both hands and feet.11 This protocol was further refined by testing CDT and WDT, at both hands and feet using only MLe.11 Recently the new Besta criteria recommended to perform CDT and WDT measurements bilaterally only at the feet, using both MLi and MLe.7 Several recent studies of diagnosing SFN have shown a lack of uniformity in TTT testing15–17 which makes it a challenge to compare the data. However, what all the studies have in common is that they defined “abnormal QST” when one of the parameters measured was abnormal. It is known that the chance of finding an abnormality increases with increasing number of measurements. With this study we first wanted to investigate whether QST could benefit from a new approach focusing on the balance between the number of measurements, depending on the selection of parameters and measuring sites, and on number of abnormalities (NOAs). Second, we wanted to address the role of MLe in possible desensitization during TTT measurements. Methods Ethics The study protocol was approved by the local Ethics Committee (Medical Research Ethics Committees United, Nieuwegein, the Netherlands R19.080). The study was conducted in accordance with the Declaration of Helsinki and GCP guidelines. Verbal and written consent was obtained before starting the study. All data have been collected and saved in a database (RedCap). Design This was a prospective, cross-sectional observational study. Sarcoidosis patients aged 18-75 years with and without clinical signs of SFN, were included between January 2021 and September 2022 at the outpatient clinic of the St. Antonius Hospital, a tertiary referral center for sarcoidosis and ILD in the Netherlands. Additionally, healthy controls were included, consisting of partners of participants and colleagues. Sarcoidosis was diagnosed using the criteria of the American Thoracic Society/European Respiratory Society.18 The exclusion criteria were: polyneuropathy, other diseases with a risk of developing neuropathy or polyneuropathy, neurological diseases affecting sensory nerve function, language barriers, mental health problems, pregnancy, glucose intolerance, vitamin B12 deficiency and excessive alcohol intake as judged by the treating physician. Neuropathy Assessment All participants underwent detailed assessment of SFN by a neurologist, and medical history assessing any type of annoying spontaneous, evoked pain sensations or other symptoms related to SFN. Neurological physical examination was used for cerebellar, large nerve fiber and small nerve fiber assessment, as described in Table 1. Patients completed the small fiber neuropathy screening list (SFNSL)19 to quantify their somatic and autonomic symptoms. Sensory and motor nerve conduction studies were performed to exclude large fiber involvement. Surface recording electrodes with standard placement were used to measure compound muscle action potential, sensory nerve action potential and nerve conduction velocity. Motor nerve conduction was assessed in peroneal and tibial nerves and sensory nerve conduction was assessed in the sural nerve. 5 83 5
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