The Importance of an Oral Glucose Tolerance Test for People with Cystic Fibrosis

Cystic fibrosis is a genetic condition that primarily affects the lungs and digestive system, but it also has an impact on glucose metabolism. Over time, damage to the pancreas caused by thick, sticky mucus can impair insulin production, leading to a condition known as cystic fibrosis diabetes (CFD).
CFD can be difficult to detect in its early stages because it often develops gradually and without obvious symptoms. However, catching it early is essential - prompt treatment can improve weight, lung health, and quality of life. This is where the oral glucose tolerance test (OGTT) plays a vital role.

Why the OGTT is the gold standard for CFD diagnosis

The OGTT involves measuring blood glucose levels after fasting and again after drinking a standard glucose solution. For people with cystic fibrosis, this test is far more sensitive than routine fasting blood glucose checks or HbA1c measurements. CFD often begins with intermittent spikes in blood sugar, which can be missed if only a single fasting measurement is taken. The OGTT captures these fluctuations, enabling clinicians to detect problems early - often before the patient notices any symptoms.
Guidelines from the Cystic Fibrosis Foundation recommend that everyone with cystic fibrosis aged 10 years and over should have an OGTT annually to screen for CFD. This regular monitoring is essential because the prevalence of CFD increases with age, and even mild glucose abnormalities can contribute to poorer health outcomes if left unmanaged.

Challenges of traditional in-clinic testing

Despite its importance, completing an OGTT can be difficult for people with cystic fibrosis. The test typically requires a two-hour visit to a clinic or hospital after an overnight fast. For patients who already face a heavy treatment burden - including daily physiotherapy, inhaled medications, enzyme supplements, and frequent medical appointments - this can be logistically and physically demanding.

Travel to a clinic may also increase exposure to respiratory pathogens - something cystic fibrosis patients must carefully avoid due to their higher vulnerability to infections. Even a routine trip to a hospital waiting area can carry significant infectious disease risks. Add in the fact that people with cystic fibrosis often experience fatigue and fluctuating health, and it’s easy to see why completing an OGTT can be challenging.

Bringing the OGTT home

With GTT@home, it’s now possible for people with cystic fibrosis to complete an OGTT safely and conveniently without leaving home. The test kit contains everything needed to complete the OGTT procedure, with clear instructions and remote support. Blood samples are taken at the required time points and analysed immediately, ensuring the same clinical accuracy as an in-clinic test.

For cystic fibrosis patients, the benefits are significant: no risk of cross-infection in healthcare settings, no travel fatigue, and the ability to fit the test around daily routines. Most importantly, it helps ensure that annual screening for CFD can happen reliably and comfortably - leading to earlier diagnosis and better long-term health outcomes.