The calculator in question is the World Health Organization (WHO) Criteria for Overt Primary Myelofibrosis. This diagnostic criteria is specifically used for patients suspected of having primary myelofibrosis, a rare bone marrow disorder that disrupts the body's normal production of blood cells.

The WHO Criteria for Overt Primary Myelofibrosis is clinically useful in diagnosing primary myelofibrosis by identifying key features of the disease. These include megakaryocytic proliferation and atypia, accompanied by either reticulin and/or collagen fibrosis, or, in the absence of significant reticulin or collagen fibrosis, the presence of an increased number of large, atypical megakaryocytes. Other criteria include not meeting WHO criteria for BCR-ABL1 positive chronic myeloid leukemia, polycythemia vera, or primary thrombocythemia.

Exclusion criteria for the use of this calculator would be patients who do not exhibit the necessary clinical, pathological, or molecular features indicative of primary myelofibrosis. Additionally, patients who meet the criteria for other myeloproliferative disorders would also be excluded from this diagnostic criteria.

WHO criteria for overt primary myelofibrosis

# Criteria
 # Major criteria
A. Presence of megakaryocytic proliferation and atypia, accompanied by either reticulin and/or collagen fibrosis grades 2 or 3
B. Not meeting the World Health Organization criteria for essential thrombocythemia, polycythemia vera, BCR-ABL11 chronic myeloid leukemia, myelodysplastic syndromes, or other myeloid neoplasms
C. Presence of JAK2, CALR, or MPL mutation or in the absence of these mutations, presence of another clonal marker, or absence of reactive myelofibrosis
# Minor criteria (presence confirmed in 2 consecutive determinations)
D. Palpable splenomegaly
E. Anemia not attributed to a comorbid condition
F. White blood cell count >= 11×10**9/L
G. Lactate dehydrogenase increased to above upper normal limit of institutional reference range
H. Leukoerythroblastosis

# Conditions
- (A and B and C) and (D or E or F or G or H)
- true