The calculator in question is the Classification Criteria for Antiphospholipid Syndrome, also known as the Sydney Criteria. This scoring system is used specifically in patients suspected of having antiphospholipid syndrome (APS), a disorder of the immune system that causes an increased risk of blood clots.

The Sydney Criteria is clinically useful in diagnosing APS and determining the need for anticoagulant therapy. It includes both clinical criteria (vascular thrombosis and pregnancy morbidity) and laboratory criteria (presence of antiphospholipid antibodies). A diagnosis of APS requires at least one clinical and one laboratory criterion to be met.

Exclusion criteria for the use of the Sydney Criteria include the presence of other conditions that could explain the clinical manifestations, such as systemic lupus erythematosus. Additionally, the antiphospholipid antibodies should be present on two or more occasions at least 12 weeks apart, so transient presence of these antibodies does not meet the criteria.

Classification criteria for antiphospholipid syndrome (Sydney criteria)

# Description:
The calculator in question is the Classification Criteria for Antiphospholipid Syndrome, also known as the Sydney Criteria. This scoring system is used specifically in patients suspected of having antiphospholipid syndrome (APS), a disorder of the immune system that causes an increased risk of blood clots.

The Sydney Criteria is clinically useful in diagnosing APS and determining the need for anticoagulant therapy. It includes both clinical criteria (vascular thrombosis and pregnancy morbidity) and laboratory criteria (presence of antiphospholipid antibodies). A diagnosis of APS requires at least one clinical and one laboratory criterion to be met.

Exclusion criteria for the use of the Sydney Criteria include the presence of other conditions that could explain the clinical manifestations, such as systemic lupus erythematosus. Additionally, the antiphospholipid antibodies should be present on two or more occasions at least 12 weeks apart, so transient presence of these antibodies does not meet the criteria.
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# Inputs:
# Laboratory criteria (present on >= 2 occasions at least 12 weeks apart)
A. Positive lupus anticoagulant 
B. Elevated anticardiolipin antibodies
C. Elevated anti-beta-2-glycoprotein antibodies
# Thrombotic criteria
D. Arterial thrombosis
E. Venous thrombosis
F. Small vessel thrombosis
# Obstetrical criteria
G. >= 3 unexplained miscarriages at < 10 weeks gestation
H. >= 1 unexplained fetal death > 10 weeks gestation
I. >= 1 preterm birth before 34th week of gestation due to preeclampsia or placental insufficiency
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# Scoring:
- If (A or B or C) and ((D or E or F) or (G or H or I)), then Diagnostic criteria are met
- If true, then Diagnostic criteria are not met)