D-dimer for the exclusion of cerebral venous thrombosis: a meta-analysis of low risk patients with isolated headache.

BACKGROUND: Patients with isolated headache may have cerebral venous thrombosis (CVT). D-dimers are proven sensitive in excluding deep venous thrombosis (DVT) and pulmonary embolism (PE) in low risk patients. We aimed to determine whether D-dimer may play the same role in low risk CVT patients with isolated headache.

METHODS: We included consecutive patients suspected of CVT from our teaching hospital with isolated headache, a normal neurological examination and normal standard head CT in whom D-dimer was determined. Additionally we did a systematic review on articles describing consecutive patients suspected of CVT with isolated headache and their D-dimer values. CVT was investigated with CT or MR venography in all patients.

RESULTS: A total of 636 consecutive patients were collected from our own data and the literature search. Of 45 CVT patients one had a negative D-dimer (7.5 %). Sensitivity of D-dimer for diagnosing CVT was 97.8 % (95 % CI: 88.2-99.6 %), specificity was 84.9 % (95 % CI: 81.8-87.7 %), positive predictive value was 33.1 % (95 % CI: 25.2-41.7 %), negative predictive value was 99.8 % (95 % CI: 98.9-100 %). Another 56 isolated headache CVT patients were identified in literature, lacking consecutive isolated headache controls. Sensitivity of D-dimer for diagnosing CVT including these patients was 87.1 % (95 % CI: 79.0-93.0 %).

CONCLUSIONS: D-dimers have a high negative predictive value in patients with isolated headache for excluding CVT. Sensitivity is lower but comparable to the values accepted in PE and DVT. Low risk patients were defined as headache patients with a normal neurological examination, normal standard head CT and absence of risk factors such as pregnancy or puerperium. Normal D-dimers in these patients may reduce unnecessary imaging, making it a potential valuable marker.