Analysis of an electrical impedance spectroscopy system in short-term digital dermoscopy imaging of melanocytic lesions.

BACKGROUND: Electrical impedance spectroscopy (EIS) is a noninvasive diagnostic technique that measures tissue impedance.

OBJECTIVES: To evaluate the effect of adding an EIS measurement at baseline to suspicious melanocytic lesions undergoing routine short-term sequential digital dermoscopy imaging (SDDI).

METHODS: Patients presented with suspicious melanocytic lesions that were eligible for short-term SDDI (with no clear feature of melanoma on dermoscopy). EIS measurement was performed at the first visit following dermoscopic photography. Normally, an EIS score of ≥ 4 is considered positive; however, this protocol investigated a higher cut-off in combination with SDDI. When the EIS score was ≥ 7 the lesion was excised immediately owing to the high risk of melanoma. Lesions with a score < 7 were monitored with standard SDDI over a 3-month period.

RESULTS: From a total of 160 lesions analysed, 128 of 154 benign lesions received an EIS score of 0-6, giving a specificity of the EIS method for the diagnosis of melanoma of 83·1% [95% confidence interval (CI) 76·3-88·7]. Five of the six melanomas found in this study had an EIS score ≥ 7, with a sensitivity for melanoma diagnosis of 83·3% (95% CI 35·9-99·6). When EIS 0-6 lesions were subsequently followed up with SDDI, one additional melanoma was detected (EIS = 6) giving a sensitivity for the diagnosis of melanoma overall of 100% (95% CI 54·1-100; six of six malignant melanomas excised) and a specificity of 69·5% (95% CI 61·5-76·6; 107 of 154 benign lesions not excised).

CONCLUSIONS: If utilizing a protocol where an EIS score ≤ 3 requires no SDDI and ≥ 7 requires immediate excision, it reduced the need for SDDI by 46·9% (n = 75/160; 95% CI 39·0-54·9).