Assessing the Minimum Detectable Change Capability of Tissue Dielectric Constant Values as Applicable to Edema and Lymphedema Measurements

Nova Southeastern University, Davie, Florida, USA

Objective. This study was conducted to determine the minimum detectable change (MDC) capabilities of two tissue dielectric constant (TDC) measurement device types using test-retest measurements from which intraclass correlation coefficients (ICC) could be estimated. Background. TDC values of skin are measures of localized water content used as a tool to help detect, characterize, and assess treatment-related changes to edema and lymphedema. However, there has never been a systematic study of in vivo reliability aspects (such as MDC) or comparison of the two types of probes in use: the moisture meter D (MMD) and the moisture meter compact (MMC). Methods. Forty volunteer subjects participated, and two measurers (M1 and M2) used each of the TDC devices to measure TDC in triplicate sequentially and bilaterally at the anterior forearm, hand palmar mid-thenar eminence, and hand dorsum mid-web, and were completed by each measurer twice constituting test-retest values (T1 and T2). ICC2,1 and MDC at 95% confidence were determined for each site, probe, and for both absolute TDC values and inter-side TDC ratios. Results. MDC values for absolute TDC values ranged from 2 to 9 TDC units, and for inter-side ratios ranged from 5.3% to 8.0% depending on anatomical site and the specific TDC probe used. Values obtained for the ICC2,1 ranged from 0.765 to 0.982. Conclusion. The MDC values for absolute TDC or inter-side TDC ratios obtained in this study provide useful estimates of the MDC that reliably represents a real difference or change when measuring TDC in research or clinical situations.