A clinical study has shown that doctors are significantly more likely to suspect the presence of deep vein thrombosis (DVT) than it actually exists. The primary reason for this lies in the relatively nonspecific symptoms. Patients often report feelings of heaviness or tightness in the legs or swelling. These complaints can occur in a similar combination with many different conditions. Consequently, primary care diagnostics require a structured approach:
First, the family doctor assesses the likelihood of DVT using the so-called Wells Score. This tool calculates the probability of occurrence based on the following risk factors:
- Is there an active cancer diagnosis?
- Recent surgery or prolonged immobilization of the leg?
- Bed rest for more than 3 days or surgery within the last 3 months?
- Tenderness along the course of the deep veins?
- Swelling of the entire leg?
- Circumference of the affected leg more than 3 cm larger than the unaffected leg?
- Unilateral edema?
- Prominent superficial veins?
- Previous thrombosis or embolism?
Different versions of the Wells Score exist. The further medical approach depends on the number of questions answered positively:
If only one or none of the above criteria apply, D-dimers—clotting breakdown products in the blood—can be measured. If these are not elevated, thrombosis is unlikely and no further investigation is needed. If two or more criteria are met, the probability is already at least 55%. In this case, a compression ultrasound of the legs should be performed immediately. Not all thrombi are directly visible on ultrasound. Therefore, the doctor also compresses the vein with the ultrasound probe. If the vein is occluded by a thrombus, it cannot be compressed. Some thrombi are initially too small to be detected sonographically. Current guidelines therefore recommend a follow-up examination within one week to identify growing thrombi.