ASA-M2 is an instrument that measures admittance of the skin when low and high frequency alternating voltages are applied to the skin surface. This instrument records three parameters for the water content (W
μS),barrier function (P%), and thickness of the stratum corneum (T
μm), of which the latter two are theoretical values based on a unique equivalent circuit skin model. We evaluated the reliability of this instrument by measuring these parameters on various skin lesions (30 sites), such as atopic dermatitis, and their normal skin controls (30 sites) and tape-stripped skin (24 sites) using this instruments and two other standard machines, skin surface hygrometer SKIKON
®, and DERMALAB
® for transepidermal water loss (TEWL) measurement. As a result, a good correlation (r=0.76, P<0.001) was found between W and admittance values by SKIKON
® on all measured data. There was also a weak but significant correlation (r=0.28, P<0.01) between P and TEWL measured with DEMALAB
®. This correlation coefficient became far better (r=0.55, P<0.001) when only data on skin lesions and tape-stripped skin were selected. No significant correlation was found between P and TEWL concerning the data measured on the normal control skin, indicating that the parameter P is not so sensitive to be able to evaluate barrier function of normal skin, although it may be useful for detecting damaged barrier function in skin lesions. The absolute values of T seemed to be unreliable because of the gap between obtained data and expected values, although it tended to roughly change as it would be expected. This parameter value, therefore, should be regarded as a relative or arbitrary unit. This instrument may be suitable when a researcher who needs both skin hydration and TEWL data but cannot afford two types of instruments.
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