No added value of the methionine loading test in assessment for venous thrombosis and cardiovascular disease risk

Homocysteine is a risk factor for cardiovascular disease and venous thrombosis. Clinical guidelines differ in their recommendation whether or not to measure homocysteine after methionine loading. In this study, we investigated the added value of the methionine loading test next to fasting homocysteine levels for identifying subjects at risk for venous thrombosis or cardiovascular disease, using Receiver Operating Characteristic (ROC) curves. The analysis was performed in 185 patients with recurrent venous thrombosis, 130 patients with cardiovascular disease and 601 controls. The discriminatory power of the fasting homocysteine measurement alone for identifying subjects at risk of venous thrombosis expressed as the area under the ROC curve (AUC) was 0.61 (95%Cl 0.56-0.66). Using both a fasting homocysteine measurement and a methionine loading test together yielded a similar AUC of 0.65 (95% Cl 0.60-0.69), indicating no added value of methionine loading next to fasting homocysteine measurement in identifying subjects at risk for thrombosis. Similar results whether found for cardiovascular disease, with an AUC of 0.62 (95%Cl 0.57-0.67) for the fasting homocysteine measurement alone and an AUC of 0.62 (95%Cl 0.57-0.67) for the combination of both the fasting and the postload homocysteine measurement. The methionine loading test has no added value next to measuring fasting homocysteine levels for identifying subjects at risk for venous thrombosis or cardiovascular disease and for that reason should not be used in clinical practice.