Celiac disease (CD) is an autoimmune condition where consuming gluten, a protein found in wheat, rye, and barley, triggers an immune response. This response mistakenly attacks the small intestinal villi, which are responsible for nutrient absorption. Because CD has a strong hereditary component, the diagnosis of a family member, particularly a sister, significantly changes an individual’s personal risk profile. This heightened risk makes screening a medically recommended step.
The Genetic Risk for First-Degree Relatives
Celiac disease has a powerful genetic link that strongly influences the risk for family members. First-degree relatives (parents, children, and siblings) of someone with CD have a significantly elevated lifetime risk, estimated between 7% and 15%. This is much higher than the general population’s risk of about 1%.
The genetic predisposition is tied to specific human leukocyte antigen (HLA) genes, primarily HLA-DQ2 and HLA-DQ8. Nearly all individuals with CD carry one or both of these genes. However, these genes are also present in up to 40% of the general population who will never develop the disease. If an individual does not carry HLA-DQ2 or DQ8, their chance of developing CD is extremely low (less than 1%), effectively ruling out the disease.
When Should Screening Occur?
Given the elevated genetic risk, screening is recommended for first-degree relatives, even if they show no obvious symptoms. Many cases are “silent” or asymptomatic, meaning intestinal damage occurs without typical digestive distress. Untreated silent CD can still lead to serious complications, including nutrient deficiencies and osteoporosis.
Testing should not depend solely on symptoms, though signs like unexplained fatigue, iron-deficiency anemia, or new digestive issues should trigger immediate testing. For asymptomatic relatives, medical consensus suggests periodic monitoring. Experts often recommend repeating screening blood tests every three to five years, or sooner if associated conditions, such as autoimmune thyroid disease, develop.
Navigating the Diagnostic Steps
The diagnostic process requires the individual to be actively consuming gluten. The first step is typically a serology blood test, which measures specific antibodies, most commonly tissue transglutaminase immunoglobulin A (tTG-IgA). Regular gluten consumption is crucial for accuracy, as a gluten-free diet can lead to a false-negative result.
If serology is positive, a definitive diagnosis requires an upper endoscopy with a small intestine biopsy. During the endoscopy, a gastroenterologist takes tissue samples from the small intestine. These samples are examined for characteristic signs of celiac disease, such as villous atrophy (damage to the villi responsible for nutrient absorption).
Genetic testing for HLA-DQ2 and HLA-DQ8 can be used if the individual has stopped eating gluten or if other results are inconclusive. A negative HLA test effectively rules out celiac disease, eliminating the need for further monitoring. A positive genetic test only indicates risk, however, and still requires serology and potentially a biopsy to confirm active disease.
Interpreting Test Results and Follow-Up Care
The results of initial screening tests fall into three main categories, each guiding future action. A positive serology test followed by a positive biopsy confirms celiac disease, requiring the immediate adoption of a strict, lifelong gluten-free diet. Following the diet allows the small intestine to heal, and resolution is monitored through follow-up blood tests.
A negative serology result indicates the disease is not currently active, but the underlying genetic risk remains. This individual is considered at risk for “latent” celiac disease, meaning they have the necessary genes but no current intestinal damage. Ongoing, periodic re-testing is recommended because celiac disease can develop at any point in life.
In some instances, serology may be positive while the biopsy is normal, referred to as potential celiac disease. These individuals require continued vigilance and regular monitoring, as they may progress to full-blown celiac disease later. All results should be discussed with a healthcare provider who can create a personalized long-term monitoring schedule.