The detection of cervical intraepithelial neoplasia by electrical impedance spectroscopy: the effects of acetic acid and tissue homogeneity.

OBJECTIVE

To evaluate the efficacy of an electrical impedance probe (Epitheliometer) in the diagnosis of high grade cervical intraepithelial neoplasia (CIN) in women referred with cervical smear abnormalities and to assess the effect of acetic acid (AA) and tissue boundaries on the measurements.

METHODS

A prospective observational study was undertaken in the colposcopy clinic. One hundred and sixty-five women, either with a clinical indication or abnormal cervical cytology, were recruited into the study. A pencil type probe was used to record impedance spectra from 12 points on the cervix before and after the application of 5% AA. Spectra were also recorded from tissue boundaries. Colposcopic examinations, including probe positioning, were video recorded to allow for correlations between histopathological diagnosis of colposcopically directed biopsies, colposcopic impression and the diagnosis based on impedance measurements.

RESULTS

Receiver operating characteristic (ROC) curves were derived. The areas under the curves (AUCs) to discriminate original squamous from high grade CIN were 0.80 (pre AA) and 0.79 (post AA). Comparison of these curves showed no significant difference, indicating that application of AA does not produce a large change in spectra. The probe could distinguish tissue boundaries from homogeneous tissue points.

CONCLUSION

The Epitheliometer has the potential to be used as an adjunct to colposcopy in the diagnosis of high grade CIN. It has the advantage of real time results, decreasing the need for diagnostic cervical biopsies, and facilitates a wider use of the 'see and treat' policy without the risk of overtreatment.