Reproducibility and variability of transepidermal water loss measurement. Studies on the Servo Med Evaporimeter.

Recording technique and accuracy of the Servo Med EP1 evaporimeter were studied. The technical accuracy of this equipment was found high with a coefficient of variation of 3.3%. Measurements of transepidermal water loss (TEWL) were performed on the palm of the hand and on the flexor side of the forearm in 10 healthy volunteers. Continuous registrations were undertaken for a three-minute period and repeated immediately thereafter. Values reached a linear state 30 sec after application of the probe. The variation of TEWL in relation to time was determined in the same individuals. Measurements were repeated after 1 hour and 24 hours. In conclusion, though the TEWL as measured by the Servo Med evaporimeter shows a considerable interindividual variation, the intraindividual variation and the variation by time are relatively minor. We recommend that more detailed studies are based on paired observations, with recordings read 30 sec after application of the probe onto the skin.