The Marfan syndrome systemic scoring calculator assesses various physical signs to evaluate the involvement of Marfan syndrome characteristics. It accepts a series of true or false responses for specific clinical features and translates these responses into numerical scores. The aggregate of these scores determines the extent of systemic involvement.

Essential clinical features and their scores are as follows:

| Clinical Sign                                                                                     | Score |
|---------------------------------------------------------------------------------------------------|-------|
| Wrist or thumb sign                                                                               | 1     |
| Wrist and thumb sign                                                                              | 3     |
| Reduced elbow extension                                                                           | 1     |
| Reduced upper segment/lower segment ratio, increased arm/height ratio without severe scoliosis    | 1     |
| Hindfoot deformity                                                                                | 2     |
| Plain pes planus                                                                                  | 1     |
| Protrusio acetabuli                                                                               | 2     |
| Pectus carinatum deformity                                                                        | 2     |
| Pectus excavatum or chest asymmetry                                                               | 1     |
| Pneumothorax                                                                                      | 2     |
| Dural ectasia                                                                                     | 2     |
| Scoliosis or thoracolumbar kyphosis                                                               | 1     |
| Facial features including 3 or more of dolichocephaly, enophthalmos, downslanting palpebral fissures, malar hypoplasia, retrognathia | 1     |
| Skin striae                                                                                       | 1     |
| Myopia greater than 3 diopters                                                                    | 1     |
| Mitral valve prolapse                                                                             | 1     |

For the computation, each clinical feature present (i.e., set to true) contributes its specific score to the total. The score thus ranges from 0, indicating no identified features, to a maximum of 23, when all described signs are present.

The interpretation of the calculated score is straightforward:
- If the score is 7 or higher, it indicates significant systemic involvement of Marfan syndrome. This suggests that the individual expresses a substantial number of features characteristic to the condition.
- A score of 6 or below indicates no systemic involvement, meaning that while some features may be present, they do not collectively amount to significant systemic features of Marfan syndrome.

These results—the total score and its interpretation—aim to guide screening and diagnosis, reflecting the potential presence of systemic features associated with Marfan syndrome.

The calculator in question is the Scoring of Systemic Features of Marfan Syndrome. This scoring system is specifically designed for patients suspected of having Marfan syndrome, a genetic disorder that affects the body's connective tissue. 

The clinical utility of this calculator is to aid in the diagnosis of Marfan syndrome. It does this by scoring the presence and severity of various systemic features commonly associated with the condition, such as skeletal abnormalities, ocular lens dislocation, and cardiovascular issues. 

The score is based on a point system, with a higher score indicating a higher likelihood of Marfan syndrome. A score of 7 or more is considered a positive systemic score, which is one of the major criteria for diagnosing Marfan syndrome according to the revised Ghent nosology.

There are no specific exclusion criteria for the use of this calculator. However, it should be noted that a lower score does not definitively rule out Marfan syndrome, especially in younger patients who may not yet have developed all the systemic features of the condition. Therefore, clinical judgment and further diagnostic testing may still be necessary.

Scoring of systemic features of Marfan syndrome