What is an esophageal string test?

An esophageal string test is a cutting-edge, minimally invasive test offered at Children’s Hospital of Philadelphia (CHOP) for patients diagnosed with eosinophilic esophagitis (EoE), a chronic allergic inflammatory disease of the esophagus, the muscular tube that carries food from the throat to the stomach. 

For this procedure, patients swallow a pill-sized capsule (about the size of a Tic Tac^®) containing an absorbent string. Once the capsule dissolves, the string sits in the esophagus for one hour to absorb different proteins in the patient’s mucus. Then, the string is removed and sent to the lab to detect mucosal eosinophil counts and any signs of eosinophilic inflammation.

In many cases, an esophageal string test can be performed instead of a pediatric endoscopy to figure out if your child has active disease in their esophagus. The string test does not require anesthesia; therefore, preparation before and recovery after the test is typically shorter than with endoscopy.  

Recent studies showed the one-hour esophageal string test can be used in patients who have been diagnosed with EoE to accurately determine if they have active or inactive EoE. Read results from a study in the Journal of Allergy and Clinical Immunology. 

When is an esophageal string test performed?

Your child’s gastroenterologist or allergist may recommend an esophageal string test for your child as an alternative to an endoscopy to assess their current condition and determine if their EoE is active or not. This information is helpful so clinicians can adjust your child’s treatment as needed.   

An esophageal string test may be repeated as needed – typically every 6 to 12 months – instead of a follow-up endoscopy to: 

• Assess disease activity after changes in therapy 
• Figure out if esophageal inflammation is the cause of new symptoms 
• Monitor for inflammation in patients without symptoms who have been doing well on the same therapy for more than 1-2 years 

Endoscopy is still the gold standard for initially diagnosing EoE. 

Preparing for an esophageal string test

An esophageal string test is not appropriate for all patients. It is typically recommended for patients age 6 and older, although your child’s developmental level and willingness to participate will factor in whether the test is right for your child. 

To participate in the test, your child must be able to: 

• Swallow the small capsule attached to a string  
• Keep the string in their esophagus for an hour  
• Have the end of the string taped to their face 
• Sit still while the string is removed 

On the day of the esophageal string test, families are counseled to: 

• Allow their child to take any of their usual medications (but not within 2 hours of the test) 
• Not allow their child to eat 2 hours before the test 
• Not allow their child to drink anything – even water – for 1 hour before the test 

What happens during an esophageal string test? 

On the day of your child’s appointment, they should not eat or drink anything for 1 hour before coming to the appointment. 

During an esophageal string test, you or your child may be asked to hold the end of the string attached to the capsule containing a folded, absorbable string, and then your child will be told to swallow the capsule. They will be able to drink water to help the capsule go down and may continue to drink water as needed.

Once the capsule is in the esophagus, it will dissolve, leaving the string in place to absorb various proteins in your child’s mucus. With one end of the string in the esophagus, the other is taped to your child’s cheek where it will remain for an hour.

During the wait time, your child may watch TV, read or play – but is encouraged to remain relatively still to avoid disrupting the tape. If your child has an upset stomach, feels like throwing up or has any discomfort, please talk to your child’s care team at the bedside.   

After an hour, the tape is removed from your child’s cheek, and the string is pulled out of their mouth. While removing the string is not painful, it can feel strange to some children. We often encourage patients to say “ahh” to open the airway and distract the child during the quick removal process. 

Once the string is removed, it is sent to the lab where samples are tested for signs of eosinophilic inflammation. 

What happens after the esophageal string test

After the esophageal string test, your child can return to their typical activities immediately. They can eat and drink normally and should have no side-effects from the procedure.  

In rare cases, a child may have troubling symptoms after an esophageal string test. Please contact your child’s doctor if they have:  

• Trouble breathing or swallowing 
• Persistent sore throat 
• Fever 
• Chest or stomach pain 

Benefits of an esophageal string test

The benefits of an esophageal string test include: 

• The procedure is noninvasive and painless.  
• The procedure precisely detects inflammation levels to determine disease activity. 
• It does not require your child to undergo anesthesia, making the procedure safer and recovery quicker. 
• It can be performed instead of repeated endoscopies, which require extra time scheduling and performing – leading to missed time in school, work and activities. 

Why choose CHOP for an esophageal string test?

CHOP’s Center for Pediatric Eosinophilic Disorders provides expert care and treatment for more than 1,500 children each year with eosinophilic esophagitis (EoE) and related eosinophilic disorders – serving the largest clinical population in the world. Our center is a recognized leader in pediatric EoE research, driving innovations that advance diagnosis, treatment and patient outcomes.   

One of the challenges of treating children with EoE is the need for repeated endoscopies to assess disease levels and determine if treatments are working. That’s why our clinical and research teams have carefully studied the esophageal string test as a potential alternative. After extensive research, we feel confident the esophageal string test provides precise inflammation levels in the esophagus – allowing us to know if a treatment is working or if we should revise the therapy to address the cause of a patient’s specific inflammation. For patients with more complex disease, we also offer transnasal esophagogastroduodeoscopy (TNE).