The Rai Staging System for Chronic Lymphocytic Leukemia (CLL) calculator assesses the risk group classification based on five clinical input parameters: enlarged lymph nodes, enlarged spleen, enlarged liver, anemia, and thrombocytopenia. Based on the patient's responses to these parameters, the calculator determines the risk group and the associated overall survival expectation.

Inputs:
1. Enlarged lymph nodes: No (A) or Yes (B)
2. Enlarged spleen: No (C) or Yes (D)
3. Enlarged liver: No (E) or Yes (F)
4. Anemia: No (G) or Yes (H)
5. Thrombocytopenia: No (I) or Yes (J)

Computation process:
The calculator evaluates combinations of these categorical inputs to classify the patient into one of three risk categories.

1. Low risk group: This is determined if there is no presence of enlarged lymph nodes, anemia, or thrombocytopenia (A && G && I). Individuals in this group have an average overall survival of more than 10 years.

2. Intermediate risk group: Patients fall under this category if they exhibit combinations of symptoms such as:
   - Presence of at least one of enlarged lymph nodes, spleen, or liver, and absence of anemia and thrombocytopenia (B && D && F && G && I), or 
   - Presence of enlarged spleen, with or without enlarged lymph nodes and liver, and absence of anemia and thrombocytopenia (D && A/B && E/F && G && I).
   In this group, the expected overall survival is around 7 years.

3. High risk group: Patients are classified in this group if they have:
   - Presence of any combination of symptoms, but show anemia and/or thrombocytopenia (A/B && C/D && E/F && H && I), or 
   - Presence of combinations including enlarged lymph nodes, spleen, or liver, with or without anemia, and thrombocytopenia (B/D/F && G/H && J).
   This group has a significantly shorter overall survival, averaging less than 4 years.

The Rai Staging System for Chronic Lymphocytic Leukemia (CLL) is a clinical tool used to classify and stage patients with CLL, a type of blood and bone marrow cancer. This system is specifically applicable to patients diagnosed with CLL and helps in predicting the disease progression and survival outcomes.

The Rai Staging System stratifies patients into three risk groups: low (Stage 0), intermediate (Stages I and II), and high risk (Stages III and IV), based on the presence of lymphocytosis, lymphadenopathy, hepatomegaly, splenomegaly, and anemia or thrombocytopenia. 

The clinical utility of this calculator is to guide treatment decisions and prognosis. For instance, patients in the low-risk group may not require immediate treatment and can be closely monitored, while those in the high-risk group may require aggressive treatment.

There are no specific exclusion criteria for the use of the Rai Staging System. However, it may not be as applicable or accurate in patients with atypical presentations of CLL or in those with co-existing hematological disorders.