Novel ZedScan beneficial as adjunct to Colposcopy in the detection of cervical neoplasia: IJOGR

Despite the existence of national guidelines, the screening coverage in India is appalling and is mainly attributed to inequality between infrastructure, resources and outsized population.

The clinical screening programmes generally involve Pap smear evaluation and/or screening clinically through colposcopy. However, the clinical performance of colposcopy is subjective and variable, dependent on factors including disease prevalence and training.

Recently, Zilico has developed a device (the ZedScan) that uses cervical electrical impedance spectroscopy (EIS) during colposcopy to help locate cancer or pre-cancerous lesions. The device is claimed to enable clinicians to improve the diagnostic accuracy of colposcopy, meaning effective medical decisions with a need for fewer biopsies and a reduction in over-treatment of mild abnormalities. EIS works on the principle that all tissues have an electrical impedance. This impedance varies depending on the type of tissue and its components. At high frequencies, more than 1 ghz current enters the cell membrane. The nuclear size and cell volume determine the impedance to the flow of the current.

A study was done by Shalini Vasudeva and Ragini Thapa to evaluate and assess the accuracy of the detection of cervical intraepithelial neoplasia using electrical impedance spectroscopy with colposcopy. It was a prospective study done on a sample size of 200 patients. The patients were selected from amongst all the patients attending the Department of Obstetrics & Gynaecology, Base Hospital, Delhi Cantt, either with a clinical indication or an abnormal cervical cytology. All such cases were recruited into the study with histopathology as a gold standard.

Electrical impedance spectroscopy was carried out by specialised diagnostic system. It consists of a portable handheld device which has a pencil shaped probe on which a single-use EIS sensor is mounted. This sensor incorporates four gold electrodes which record impedance spectra from 12 points on the cervix. Spectra were also recorded from tissue boundaries. The probe was used to take a total of 12 measurements from the cervix. Impedance measurements were automatically transferred to software on a laptop. Colposcopy was then performed, and cervical biopsies were taken wherever clinically indicated.

Mean age of patients was 37.48±6.3 years. Almost all (98.5%) the test patients were married. Majority of women were educated up to graduation or above (51%) followed by those educated upto 8th standard (n=53; 26.5%) and those educated upto secondary level (22.5%).

Histopathologically, a total of 26 cases were positive and 174 were negative. As compared to histopathology, ZedScan had 11 true positive, 5 false positive, 15 false negative and 169 true negative cases.

Correspondingly, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy value of ZedScan for any grade of neoplasia was 42.3%, 97.1%, 68.8%, 90.9% and 90% respectively.

In present study for any abnormality (any CIN) detected during colposcopy and EIS independently had a sensitivity & specificity of 69.2% & 93.1% and 42.3% & 97.1% respectively.

However, when EIS was used as an adjunct to colposcopy there as an appreciable increase in the sensitivity to 80.8% while maintaining the specificity at 91.4%.

For higher grade CIN too, colposcopy and EIS independently had a sensitivity & specificity of 64.3% & 94.6% and 64.3% & 96.2% respectively, which on the combination of two reached to 85.7% & 90.9% respectively, thus demonstrating that for neoplasms in general and that of higher grades of neoplasms, the combined use of colposcopy with ZedScan helps to elevate the sensitivity and specificity substantially.

The findings of the study conducted thus suggest that ZedScan has a useful role as an adjunct to Colposcopy in the detection of cervical neoplasia, particularly that of high-grade CINs. However, whether the additional detection will have an economic implication remains to be examined.

Source: Vasudeva and Thapa / Indian Journal of Obstetrics and Gynecology Research 2021;8(2):166–171

https://doi.org/10.18231/j.ijogr.2021.036