What,if anything,should replace the Villalta score for post thrombotic syndrome?

The post thrombotic syndrome (PTS) is a condition characterised by signs and symptoms of chronic venous insufficiency secondary to previous deep venous thrombosis (DVT). It is associated with a spectrum of clinical presentations, ranging from leg oedema to severe ulceration, and can have a profound effect on quality of life.

There is no gold standard for the diagnosis of PTS. A number of clinical scales based upon signs and symptoms can help support the diagnosis. These include the Villalta scale, Patient Reported Villalta Scale, Ginsberg Measure, Brandjes Scale, Clinical Etiological Anatomical Pathological (CEAP) Classification, Venous Clinical Severity Score (VCSS) and Widmer Classification. ¹ In 2009, the Control of Anticoagulation Subcommittee of International Society on Thrombosis and Haemostasis recommended the Villalta score to diagnose and grade patients with PTS based upon a number of advantages. The Villalta score accounts for the range and severity of symptoms, it can be used as a continuous or categorical outcome measure and correlates with health related quality of life. ² The score has been shown to be valid, easy to use, accessible and has good to excellent inter observer reliability (Spearman’s co-efficient 0.89). ³ Sensitivity and specificity, however, remain unclear. ⁴

The Villalta score has some limitations. The score is calculated at a single point in time and does not reflect the duration of symptoms and their chronicity. It does not assess PTS symptoms such as venous claudication or fluctuations in symptoms related to time of day or activities, with may lead to failure to identify PTS. ⁵ Venous claudication however may be difficult to assess in practice due to inter-rater variability. Assessment of pain alone may be sufficient to capture venous claudication. The presence of an ulcer is a binary outcome and disease severity may be overestimated in individuals with healed ulcers. Finally, the signs and symptoms assessed by the score are not specific for PTS, and cannot be differentiated from chronic venous disease (CVD) or other disease pathologies. Individuals with CVD but no history of VTE can still score moderately on the Villalta scale, and misclassification of CVD as PTS could account for a positive bias of up to 42.3% in diagnosis. ⁶

There is a clear demand by some to identify stricter criteria to assess PTS. This is challenging, as there is no gold standard for diagnosis of PTS, which could be used to compare existing or proposed diagnostic scores. Additionally, assessment of diagnostic scores for PTS will always be limited by the inability to blind examiners in clinical trials. Any diagnostic score must be easy to use, and whilst a score may benefit from including information on patient experience, this should not be limited by bias. Based on guidance from the FDA, patient reported outcome measures must be reliable, valid and able to detect change. ⁷

Additional components could be added to the Villalta score to enhance its validity. Currently, we have identified that the score should continue to be assessed over time, with healed ulcers being downgraded in severity. Review of symptoms could be extended to include fluctuations over time, as well as pressure, burning and pulsation. ⁸ The use of a concurrent venous specific quality of life questionnaire has already been recommended to strengthen validity. ¹ Adding additional components should not render the scale too cumbersome for purpose, but may be of value in the context of machine learning. Machine learning algorithms, which observe patterns in large data sets to derive rules, may in the future support clinicians in diagnosis and clinical decision making. Clinical information could be collected from patients in the community, as an ecological momentary assessment, and incorporated into the scoring system as a measure of disease progression, stability or improvement.

A greater understanding of disease pathology, chronicity, chronology and characterisation is required for diagnosis and assessment. By identifying risk factors, signs, symptoms and radiological features of PTS, an algorithm could be build for diagnosis and characterisation.

Ultrasound duplex is commonly used to visualise the deep venous system and assess vessel walls, compressibility, and retrograde flow. Imaging may be complementary to but should not replace clinical assessment, and treatment should not be based on radiological findings alone. Additionally, there is overlap between the radiological findings of CVD and PTS, and CT, MRI and venography are not sensitive to deep venous insufficiency. Imaging however may have a role in classifying individuals into anatomical subgroups at diagnosis, as recommended by the LETS classification, ⁹ or as part of a larger diagnostic database algorithm.

Alternative scoring systems are frequently utilised alongside the Villalta score. These include: CEAP; VCSS; Brandjes; Widmer; Ginsberg. With the exception of CEAP, these scores are based on the assessment of signs and symptoms at a single point in time and are therefore also unable to differentiate between CVD and PTS. It may be appropriate to use different scores at different time points. The Villalta score is sensitive to mild disease whilst the VCSS focuses on elements associated with severe disease. ¹⁰ Again, these intricacies could be incorporated into a larger diagnostic algorithm.

The diagnosis of PTS is challenging. Disease assessment is impacted by a lack of understanding of disease pathology. PTS is a clinical diagnosis and patient symptoms, signs and reported quality of life should be central to diagnosis, disease grading and treatment. A more reliable assessment of PTS may be achieved through a comprehensive scoring system that examines signs, symptoms, patient experience, type of thrombosis, location of DVT and resultant site and quantity of occlusion/reflux remaining in the limb. Greater understanding of disease pathology and more thorough diagnostic criteria may be facilitated by the use of artificial intelligence.