The NO release test as a functional reference standard for laser Doppler fluxmetry in cutaneous microangiology

Abstract

Background/aims: The application of one-dimensional laser Doppler fluxmetry (LDF) to clinical research is widespread. Large intra- and interindividual fluctuations in perfusion impede the objective evaluation of studies and hinder a standardised reproducibility. Attempts are made to minimise these biological fluctuations of the measured values by means of functional tests, standardised measuring conditions and large study populations. An intraindividual fixed standard that also facilitates interindividual comparability as a reference parameter would be desirable. Methods: By applying a nitric oxide (NO) release cream, a maximal vasodilatation is produced in a circumscribed skin area and optically registered by means of LDF. An LDF quotient is defined as a measure of the reproducibility. A total of 123 test subjects with dermatological diseases were measured at intervals of 60 min on the volar underarm on clinically normal skin with and without NO release cream. Results: The LDF quotient of the NO release test represents a stable, readily reproducible individual parameter and is appropriate as a reference standard for resting flux measurements. Therefore, we define an LDF factor that includes the maximal vasodilatation as a specific assessment characteristic and thus allows a more powerful, functionally oriented assessment of the individual measurements. Conclusion: The NO release test is appropriate as a reference standard for laser Doppler fluxmetry and realises a high reproducibility of individual measurements.