122 may be present without any association with SFN. Therefore, we identified probable SFN based on the globally recognized Besta criteria in a well-defined cohort of patients with sarcoidosis while applying strict exclusion criteria.13 Despite this general limitation, the correlation between patient-reported continuous length-dependent pain and TTT NOAs remains particularly interesting. The strength of this study is the use of diagnostic methods based on structural, functional and autonomic function assessment for comparison with a new questionnaire using patient-reported outcomes. Multimodal testing for diagnosing SFN is known to improve diagnostic accuracy, but shows poor correlation between testing modalities.16 Phenotyping based on patient-reported outcome measures now provides a better understanding of what mechanisms can be measured using different diagnostic techniques. The added value of the newly developed questionnaire is twofold. For research purposes, the SFNPQ identifies detailed patient-reported pain phenotypes that provide new insights into SFN-associated pain for specific underlying mechanisms. Patient-reported continuous non-length-dependent pain was less common in SSFN. Furthermore, the diagnostic criteria were less applicable in patients without continuous length-dependent pain. Further research is needed to identify the relationship between patient-reported pain and SFN, and to investigate the pathophysiological mechanisms of intermittent pain. Determining the pathophysiological mechanisms could help develop new diagnostic methods. Conclusion Patients with SSFN report both length-dependent and non-length-dependent pain and demonstrate a balanced presentation of intermittent and continuous pain. A novel finding is that TTT only associated with continuous length-dependent pain, suggesting that TTT could result in more false negatives in patients with pain phenotypes other than continuous length-dependent. If this is confirmed in other cohorts, it will have implications not only for diagnosis of SSFN, but for all underlying diseases in which SFN related pain presents non-length-dependent or intermittently. 7 128 7
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