Parameters:
(1) swelling of the lower leg in cm
(2) pain score
swelling of the lower leg in cm =
= MAX(0.5, (circumference of affected leg in cm) - (circumference of normal leg in cm))
|
Pain on Palpation
|
Pain on Walking
|
Pain at Rest
|
Pain Score
|
|
no
|
no
|
no
|
1
|
|
yes
|
no
|
no
|
2
|
|
yes
|
yes
|
no
|
3
|
|
yes
|
yes
|
yes
|
4
|
S/P ratio =
= (swelling of the lower leg) / (pain score)
where:
• The circumference of the lower leg is taken at a point 12 cm below the lower border of the patella with the leg extended.
• The minimum value for swelling is set to 0.5 to avoid a 0 in the numerator for the ratio.
• The authors did not do pulmonary angiography if the patient was not symptomatic. This would tend to miss small pulmonary emboli.
Interpretation:
• minimum ratio: 0.125
• maximum ratio: depends on the extent of the swelling recorded
• A silent DVT is one with a low pain score. This is associated with a higher S/P ratio for a given amount of lower leg swelling.
• One use for the score is to compare groups of patients with DVTs. A high mean ratio would indicate a larger number of silent DVTs in the group.
