The process examines potential celiac disease in a patient using a set of established criteria. These criteria, selected from predefined options, include:

- Typical symptoms like chronic diarrhea, growth faltering or weight loss, and iron-deficiency anemia
- Presence of specific IgA antibodies at high levels
- Having HLA-DQ2 or DQ8 genotypes
- Evidence of celiac enteropathy on a small intestinal biopsy
- Positive response to a gluten-free diet

The evaluation uses combinations of these criteria according to the "four out of five rule" to interpret whether celiac disease is present. Each unique combination of selected criteria informs a specific diagnosis:

- CD diagnosed: When all five criteria are satisfied or if the selection includes criteria related to symptoms, antibodies, biopsy, and response to diet.
- Seronegative CD: Detected when signs, gene markers, biopsy result, and dietary response are present, despite no antibody indication.
- Non-classic CD: Identified with antibodies, gene markers, biopsy results, and dietary response, without the typical symptoms.
- Non-responsive CD: When typical symptoms, antibodies, gene markers, and biopsy outcomes are observed, but dietary response isn't considered.
- Potential CD: Suggested when symptoms, antibodies, gene markers, and dietary response demonstrate possible celiac predisposition, without biopsy confirmation.

A summary of diagnostic rules is:

| Combination                              | Result                |
|------------------------------------------|-----------------------|
| All criteria (1, 2, 3, 4, 5) or 1, 2, 3, 5 | CD diagnosed          |
| 1, 3, 4, 5                                | Seronegative CD       |
| 2, 3, 4, 5                                | Non-classic CD        |
| 1, 2, 3, 4                                | Non-responsive CD     |
| 1, 2, 3, 5                                | Potential CD          |

This method determines the patient's celiac disease status by aligning the selected criteria with these specific categories, thereby deducing the appropriate diagnosis or whether criteria are unmet.

The calculator in question is the Diagnostic Criteria for Celiac Disease, also known as the "Four out of Five Rule". This diagnostic tool is used specifically for patients suspected of having celiac disease, an autoimmune disorder that primarily affects the small intestine.

The clinical utility of this calculator is to aid in the diagnosis of celiac disease. It is based on five criteria: typical symptoms of celiac disease, positive serology, HLA-DQ2 or DQ8 genotypes, histological signs of villous atrophy, and response to a gluten-free diet. A diagnosis of celiac disease is considered when a patient meets at least four out of these five criteria.

There are no specific exclusion criteria for the use of this diagnostic tool. However, it should be noted that this tool is not definitive and should be used in conjunction with other diagnostic methods and clinical judgment. It is also important to remember that not all patients with celiac disease present with typical symptoms, and some may be asymptomatic. Therefore, a high index of suspicion is necessary when using this tool.

Diagnostic criteria for celiac disease (four out of five rule)