The Wells' Criteria for Deep Vein Thrombosis (DVT) is a clinical prediction rule used to determine the pretest probability of DVT in patients. This calculator is applicable to patients who present with symptoms suggestive of DVT, such as leg pain, swelling, or discoloration. 

The clinical utility of the Wells' Criteria for DVT is to stratify patients into different risk categories (low, moderate, high) based on their score, which can guide further diagnostic testing. A higher score indicates a higher probability of having DVT. This can help clinicians decide whether to proceed with further diagnostic imaging, such as an ultrasound or D-dimer test.

Exclusion criteria for the use of this calculator include patients who have already been diagnosed with DVT or pulmonary embolism, those who are currently on anticoagulation therapy, and those with other conditions that could mimic the symptoms of DVT, such as cellulitis or Baker's cyst.

Wells' criteria for deep vein thrombosis

# Criteria
 ## Active cancer (treatment within the previous 6 months or current palliative care)
A. Yes (+1)
B. No (+0)
## Bedridden recently >= 3 days or major surgery within the previous 12 weeks
C. Yes (+1)
D. No (+0)
## Calf swelling > 3 cm compared to the asymptomatic side (measured 10 cm below tibial tuberosity)
E. Yes (+1)
F. No (+0)
## Collateral superficial veins (non-varicose)
G. Yes (+1)
H. No (+0)
## Entire leg swelling
I. Yes (+1)
J. No (+0)
## Localized tenderness along the deep venous system
K. Yes (+1)
L. No (+0)
## Pitting edema confined to symptomatic leg
M. Yes (+1)
N. No (+0)
## Paralysis, paresis, or recent plaster immobilization of the lower extremity
O. Yes (+1)
P. No (+0)
## Previously documented DVT
Q. Yes (+1)
R. No (+0)
## Alternative diagnosis at least as likely as DVT
S. Yes (-2)
T. No (+0)

# Conditions
- score <= 0
- score <= 2
- score >= 3
- score == 0