Reproducibility of laser Doppler imager flux measurements within ischemic or venous ulcers and adjacent skin.

Background/aims: The laser Doppler imager (LDI) is a device that maps the local distribution of the laser Doppler flux of tissues. To facilitate the interpretation of LDI measurements, we investigated their reproducibility.

Methods: We measured 10 arterial ulcers, 10 venous ulcers and their adjacent skin by the use of a LDI. The means were calculated of individual coefficients of variation ± standard error of mean (meanCV ±SEM) of measurements on the same day, on 5 different days and at specific time points (0, 30, 60, 90 and 120 min) during the application of PGE, on 2 different days.

Results: The meanCV ±SEM of measurements on the same day were 9.3±0.9% (ulcer), 9.8±0.9% (skin), and on 5 different days they were 21.9±1.9% (ulcer) and 28.6±2.4% (skin). Ulcer measurements on 5 different days were significantly more reproducible than skin measurements, if differences were calculated for all 20 patients or for the 10 patients with venous ulcers separately (P<0.05). During the application of PGE, for 120 min, meanCV ±SEM ranged from 19.2±4.0% to 26.9±5.0% (ulcer) and from 20.5±4.1% to 29.5+3.9% (skin). CV of skin measurements of all 20 patients at 0 min were significantly lower than those after 120 min of PGE(1) -application (P<0.05).

Conclusion: Our results show an excellent reproducibility of LDI measurements on a single day. The reproducibility of measurements on 5 different days or during the application of PGE1 over a period of 120 min was poorer. Because of the poorer reproducibility, more patients are needed to study long-term or drug effects.