Reading a Serology Panel

A celiac serology panel is one of the most-ordered and most-misunderstood blood tests in primary care. Reading it well requires understanding what each marker measures, and what conditions make any of them unreliable.

The first-line marker

Tissue transglutaminase IgA (tTG-IgA) is the workhorse. It is highly sensitive and specific for untreated celiac disease in patients with normal IgA levels. A clearly elevated tTG-IgA in someone eating gluten is the strongest single signal short of biopsy.

Why total IgA matters

Roughly two percent of people with celiac disease have selective IgA deficiency. In those patients, every IgA-based test reads falsely negative. That is why a complete panel always includes total serum IgA. If it is low, the lab should reflexively run IgG-based tests — DGP-IgG and tTG-IgG.

The supporting cast

• Deamidated gliadin peptide (DGP) — useful in children under two and in IgA-deficient adults.
• Endomysial antibody (EMA) — very specific, operator-dependent, often used to confirm a borderline tTG-IgA.

The single most common reason a result misleads

The patient stopped eating gluten before the test. Serology depends on an active immune response, and that response fades within weeks of going gluten-free. A negative result in someone already on the diet means nothing.

If a panel is negative but suspicion remains high, the right next step is a six-week supervised gluten challenge, not reassurance.