Beyer SE, Hunink MG, Schöberl F, von Baumgarten L, Petersen SE, Dichgans M, et al. Different Imaging Strategies in Patients With Possible Basilar Artery Occlusion: Cost-Effectiveness Analysis. Stroke. 2015
Basilar artery occlusion (BAO) is a life threatening condition. Even if treated, mortality rates are still significant. In light of this, Beyer et al evaluate the cost-effectiveness of different non-invasive imaging strategies in patients with possible BAO. Specifically, four imaging modalities were studied: non enhanced CT (NECT), duplex ultrasound (US), CT angiogram of the head (CTA), and MRI/MRA.
Beyer et al employ a decision model where NECT, CTA and MRI were evaluated separately and then compared to HECT, CTA and MRI in addition to a screening US. “Treatment” was initiated if there was a positive finding such as a stroke on MRI or e/o basilar thrombus. One month mRS score was used to measure short term outcome. A Markov model with a 1 year cycle length was developed to estimate long term outcomes and costs. Costs were based on 2013 Medicare reimbursement rates, including both technical and professional fees.
The results extrapolated from the model show that for a reference case of a 63 year old male with possible BAO, CTA dominated all other strategies. CTA proved to be the most cost effective in 96% of the simulation runs and 80% of the mild symptom analysis. The least cost effective strategy was to perform NECT alone. The results were similar for women.
Ultimately, BAO work up was most cost effective when pursuing CTA alone as the first line screening tool. Although Ultrasound is a low cost tool it is ineffective it this instance due to its’ low sensitivity for picking up a BAO, technician variance, and ultimate need to move towards pursing either an MRA or CTA. Limitations of the study include that this is ultimately a model; and it is in regards to a very rare disease which can present with vast variety of clinical symptoms. It is very important to consider the clinical picture when evaluating a BAO patient. If a patient clinically appears to have BAO (based on exam and risk factors), they should be worked up for such a process regardless. Additionally, if there are symptoms are concerning enough for a basilar thrombus, treatment can and should be pursued even prior to a CTA. In this particular example, a non contrast head CT should be pursued to rule out a bleed, and IV-tPA should be given as soon as possible. A CTA can be pursued afterwards to verify whether or not a large vessel thrombus exists in consideration of a thrombectomy. While the authors of this study modeled IV thrombolysis as a treatment, they omitted IA therapies. It would be interesting to see how the results may change with regards to cost effectiveness. I surmise, it would show a similar result.
I think it is safe to say that CTA, being fast, reliable and available at most institutions is the first line agent to ruling out a BAO; especially in someone who is of high pre-test probability of having a BAO. At this point, it will not likely change our management, but it is comforting to know that our practice of ruling a patient out for such a devastating process is also the most cost effective strategy.
It is important to note that, like other cost analyses with ultrasound (US) as a diagnostic, this study did not give ultrasound a fair chance as a lone diagnostic because a positive result triggered a CTA. Of course, US + CTA will cost more than CTA alone. In the hands of experienced sonographers and sonologists, US can provide a rapid, sensitive and specific diagnosis of basilar occlusion. Even "blind TCD" (e.g., non-Duplex) has acceptable sensitivity and excellent specificity: http://stroke.ahajournals.org/content/39/4/1197.abstract