3 The diagnostic tests

3 The diagnostic tests

Two interventions and 1 comparator were included in this assessment.

The interventions

Dynamic Spectral Imaging System (DYSIS) colposcope with DYSISmap (DYSIS Medical)

3.1 The DYSIS colposcope is a CE-marked digital video colposcope. It uses spectral imaging technology and an inbuilt algorithm to produce an adjunctive map of the cervical epithelium, known as the DYSISmap (or pseudo-colour imaging). The DYSISmap is intended to be used with colposcopy to help detect cervical intraepithelial neoplasia (CIN).

3.2 The system comprises:

  • a high-resolution digital colposcope, which incorporates an inbuilt display console and monitor for the clinician

  • an optional additional monitor that allows the patient to see the images

  • single-use or reusable specula

  • an acetic acid applicator

  • software

  • a patient database (the patient management system) that stores images and videos from a colposcopy examination and records biopsy sites.

3.3 The device can be used as a standard digital video colposcope, but the spectral imaging technology used by the DYSIS colposcope also measures the speed, intensity and duration of aceto-whitening. These parameters are used to produce dynamic curves that plot intensity against time and an inbuilt algorithm assigns each area of the cervix a colour on the DYSISmap.

3.4 The DYSISmap is displayed on the screen, overlaid on a live image of the cervix, and can be used by the colposcopist to select areas for biopsy. The colour spectrum shown on the DYSISmap ranges from cyan, which represents weak aceto-whitening, to white, which represents intense aceto-whitening. The greater the intensity of the measured aceto-whitening reaction, the greater the likelihood of an abnormality. Imaging takes 3 minutes, but the colposcopist can stop it manually. However the company recommends that the system needs at least 125 seconds of imaging to allow it to calculate and display the DYSISmap.

ZedScan I

3.5 The ZedScan I is a CE-marked electrical impedance spectroscopy (EIS) system, which is designed to be used with colposcopy to help detect high-grade CIN. The system comprises:

  • a portable handset, which takes EIS readings and displays the results to the user on an inbuilt interface

  • a docking station

  • single-use EIS sensors that are placed over the snout of the handset

  • a software application, which incorporates a database to store results and can be installed onto a personal computer.

3.6 The device uses EIS to differentiate normal, precancerous and cancerous tissue by measuring the electrical properties of the cervical epithelial cells. Electrical impedance is measured at 14 different frequencies and a spectrum is produced, which varies according to the structure and properties of the tissue. The device can be used in scanning mode or in single-point mode. During scanning mode, and after acetic acid has been applied, the single-use EIS sensors take readings from between 10 and 12 sites on the cervical transformation zone. The readings are processed by the handset using an inbuilt algorithm, which quantifies the degree of abnormality (dysplasia) at each site and compares it with a reference value to give the user a semi-quantitative result. Results are displayed to the colposcopist on the inbuilt user interface. The results show the likelihood of high-grade CIN being present at each of the scanned sites.

3.7 The results provided by the device are intended to be used to guide a colposcopist to areas that need to be biopsied, when used with standard colposcopy. It is estimated that the device takes 2 to 3 minutes to scan the cervix and display the results. The results from the ZedScan I handset are automatically uploaded to the system's database through the docking station.

The comparator


3.8 During colposcopy the cervix is assessed by a colposcopist using a colposcope, which is a low-powered microscope. The aim of colposcopy in the NHS cervical screening programme (NHSCSP) is to confirm whether a potential abnormality found by cervical screening is present, and if so, to assess the likely extent and grade of the abnormal cells. Binocular colposcopy is most often used in the NHS.

3.9 The NHSCSP's colposcopy and management guidelines (2016) state that when an adequate colposcopy has been done, that is when the transformation zone has been fully visualised, the colposcopic diagnosis should have a positive predictive value of 65% for a high-grade lesion (CIN 2 or worse [CIN 2+]).

  • National Institute for Health and Care Excellence (NICE)