Cytosponge (Medtronic) is a single-use device used to collect cells from the lining of the oesophagus. It is known as a 'sponge on a string' pill test. Cytosponge consists of a spherical sponge in a dissolvable capsule, which is attached to a thread. When the capsule is swallowed, it expands into a small, rough-textured sponge in a person's stomach. After around 5 to 7 minutes, the sponge is pulled back up, collecting some of the cells lining the oesophagus.
The collected sample is sent for laboratory analysis to detect any cell abnormalities. As a part of quality control, haematoxylin and eosin staining is done to evaluate the morphology and check the presence of gastric cells on the sample to make sure that the capsule reached the stomach. The lab test is an antibody test to identify Trefoil Factor 3 (TFF3), which is only found in precancerous cells. Cells that test positive for TFF3 are likely to come from people who have Barrett's oesophagus, which increases the risk of developing oesophageal cancer. The Cytosponge test is intended as a triage test for an endoscopy in people with heartburn or reflux symptoms who need acid-suppressant medicine.
This device is contraindicated for people who:
are experiencing dysphagia or swallowing disorders
have previously had oesophagus ablation or a mucosal resection or invasive oesophageal or gastric procedure in the past 2 months
have portal hypertension or oesophageal varices
are taking anticoagulants.
Cytosponge is a minimally invasive device to detect abnormal cells in the oesophagus. The 'pill on a string' cell collection method is novel. This is combined with an immunohistochemical assay (TFF3).
Endoscopy is the current standard practice for diagnosing Barrett's oesophagus. It allows direct visualisation of the oesophageal mucosa, specifically for assessing any changes that may indicate dysplasia or cancer in the oesophagus. During the endoscopy, samples are taken for biopsy from any abnormal areas detected. It is an invasive procedure and needs sedation. Bleeding and perforation are rare reported complications of endoscopy.
The British Society of Gastroenterology guidelines on the diagnosis and management of Barrett's oesophagus recommend that the diagnosis of Barrett's oesophagus should be confirmed histopathologically from oesophageal biopsies. The guideline notes that using an immuno-based assay shows promise for enhancing the sensitivity and specificity of a cytology collection device (Cytosponge). But, results of further trials are needed before such technologies can be recommended for use outside of research.
Cytosponge is intended for collecting surface oesophagus cells samples that are sent to the lab for analysis, like a biopsy sample. It is for people seeing their GP with heartburn or reflux symptoms needing acid-suppressant medicine.
The test can be done in primary care such as a GP practice. It is also a triage tool that can help doctors decide who needs to have a follow-up endoscopy.
The costs for standard care (diagnostic endoscopic upper gastrointestinal tract procedure with biopsy, FE21Z) is estimated to be £407 (NHS tariff 2020/21). This cost includes staffing costs, which are not included in the cost of Cytosponge.
The company states that several NHS trusts are using the technology. Two experts noted that the device is not widely used in the NHS outside of trials.
A cost-effectiveness analysis done in the US showed that Cytosponge was cost effective as a screening tool when compared with no screening and endoscopic screening. These results were sensitive to Cytosponge cost within a plausible range of values (Heberle et al. 2017).
The comparison of 6 screening tests included sedated gastroscopy, Cytosponge with TFF3 biomarker, sponge on a string with methylated DNA markers, breath testing, hospital-based transnasal endoscopy, and mobile unit-based transnasal endoscopy. The US study showed that Cytosponge had favourable incremental cost-effectiveness ratios in both population-based and gastro-oesophageal reflux disease-specific screening for Barrett's oesophagus (Sami et al. 2019).