Validation of the modified LDIFlare technique: a simple and quick method to assess C-fiber function

Abstract

Introduction: In this study we validated a modified laser Doppler imager method (mLDIf) for assessing C-fiber function and compared it to the original (oLDIf). Both measure flare size in foot skin after heating, but the mLDIf uses 47°C (vs. 44°C), making it quicker and better suited for clinical use.

Methods: To confirm that mLDIf assesses C-fiber function, 5 healthy controls (HC) were studied before and after local anesthesia (LA). Reproducibility and comparison with oLDIf was assessed in HC (n = 16). Finally, diabetes subjects with (DN(+), n = 10) and without (DN(-), n = 16) neuropathy were studied.

Results: LA almost abolished the flare (9.3 ± 3.0 cm(2) vs. 1.7 ± 0.3 cm(2), P < 0.0001). mLDIf produced larger flares (9.9 ± 3.4 vs. 5.7 ± 2.3 cm(2), P < 0.0001), but correlated with oLDIf (r = 0.81, P < 0.001). mLDIf was reduced in DN(-) (6.8 ± 2.8 vs. HC, P = 0.003), markedly so in DN(+) (2.0 ± 1.1 vs. HC and DN(-), P < 0.0001).

Conclusion: The mLDIf is a quick, practical method for assessing C-fiber function in the clinical setting.