Optimizing temperature threshold testing in small-fiber neuropathy.

INTRODUCTION: We examined optimization of a temperature threshold testing (TTT) protocol for patients with suspected small-fiber neuropathy (SFN) to lessen the burden for both patients and technicians, without sacrificing accuracy. METHODS: Data from 81 patients with SFN (skin biopsy and TTT abnormal) and 81 without SFN (skin biopsy and TTT normal) were used. Warm, cold, and heat pain sensation thresholds were determined bilaterally on the thenar eminence and foot dorsum by methods of limits and levels. Diagnostic accuracy was determined for various sensory modality combinations through comparative corresponding area under the receiver-operator characteristic curves. RESULTS: Assessment of warm and cold thresholds in all extremities by the method of levels showed the best discriminatory ability (area under the curve 0.95, sensitivity 84.2%, specificity 93.8%). CONCLUSIONS: These assessments are suggested for TTT examination in possible SFN patients. By applying this combination, the time needed for TTT can be reduced, maintaining diagnostic accuracy.

Thermal threshold testing: call for a balance between the number of measurements and abnormalities in the diagnosis of sarcoidosis-associated small fiber neuropathy.

Introduction: Several recent studies of diagnosing small fiber neuropathy (SFN) have shown a lack of uniformity in thermal threshold testing (TTT) or quantitative sensory testing (QST) which makes it a challenge to compare the data. It is known that the chance of finding an abnormality increases with increasing number of measurements. Objectives: With this study, we first wanted to investigate whether TTT 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 the method of levels (MLe) in possible desensitization during TTT measurements. Methods: One hundred seventeen participants were included (48 patients with sarcoidosis with probable SFN, 49 without SFN, and 20 healthy controls). Thermal threshold testing measurements and Small Fiber Neuropathy Screening List (SFNSL) questionnaire were used to assess SFN. Results: A combination of measuring all thermal threshold parameters at both feet except for MLe showed the best diagnostic performance. Increasing TTT NOAs correlates with the severity of SFN. Adding the SFNSL questionnaire further improves diagnostic performance. Discussion: Looking at TTT NOAs in all TTT parameters except for MLe at both feet should be considered as a new approach to improve the consistency and balance between the selection of TTT parameters, measuring sites, and definition of "abnormal QST." Moreover, the SFNSL questionnaire is a valuable tool to quantify SFN symptoms and could improve SFN diagnosis.