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Ninhydrin sweat test: a simple method for detecting antibodies neutralizing botulinum toxin type A
Bernhard Voller1, Ekaterina Moraru, Eduard Auff
1Department of Neurology, Division of Neurorehabilitation, University of Vienna, Austria. bernhard.voller@meduniwien.ac.at
Summary
A simple sweat test can detect neutralizing antibodies against botulinum neurotoxin A (BoNT/A) in cervical dystonia patients who lose treatment benefit. This economical ninhydrin sweat test (NST) offers a practical alternative to current antibody detection methods.
Area of Science:
- Neurology
- Immunology
- Clinical Diagnostics
Background:
- Secondary loss of efficacy to botulinum neurotoxin A (BoNT/A) affects approximately 5% of cervical dystonia patients.
- Neutralizing BoNT/A antibodies (BoNT/A-AB) are implicated in this treatment non-response.
- Existing tests for BoNT/A-AB are often costly or time-consuming.
Purpose of the Study:
- To develop a simple, clinically applicable method for detecting neutralizing BoNT/A-AB.
- To evaluate the efficacy of the ninhydrin sweat test (NST) for identifying BoNT/A-AB.
Main Methods:
- Adapted the ninhydrin sweat test (NST) for antibody detection.
- Tested 18 patients with cervical dystonia and suspected BoNT/A-AB using the mouse diaphragm test (MDT) and NST.
- Measured the anhidrotic area 21 days post-intradermal Dysport injection.
Main Results:
- The MDT detected positive BoNT/A-AB titers in nine patients.
- A significant negative correlation was observed between BoNT/A-AB titers and the anhidrotic area (Spearman's rho = -0.9, P < 0.0001).
- Both MDT and NST demonstrated comparable qualitative antibody detection results.
Conclusions:
- The economical NST is a potentially helpful tool for detecting neutralizing BoNT/A-AB in patients experiencing secondary non-response to BoNT/A therapy.
- The NST provides a practical alternative for antibody detection in clinical settings.
- This study highlights the utility of sweat testing in diagnosing treatment resistance.