Authors' objectives: The aim of this health technology assessment (HTA) is to compare the clinical effectiveness and safety of prehospital CT for early diagnosis and potential prehospital treatment of suspected acute stroke or severe head injury with current practice of diagnosis and treatment carried out after arrival in the hospital. Furthermore, it seeks to shed light on organizational and health economic consequences related to the implementation of prehospital CT in Norway.

Authors' results and conclusions: Clinical effectiveness and safety: Searches for primary studies resulted in a total of 2,628 unique records. Of these, 8 publications, representing 4 studies, were considered eligible for inclusion. The studies comprised two randomized controlled trials (RCTs) and one observational registry study from Germany, and a dosimetry (measurements of radiation exposure) study from the U.S. In all of these studies, the intervention consisted of an MSU for stroke. MSU care reduced the time from alarm to imaging and from alarm to thrombolysis. Based on the study findings, the difference between MSU and conventional care in mean minutes from alarm to CT was around 27 minutes (95% CI -51 to -3) (low certainty of the evidence), and from alarm to thrombolysis around 31 minutes (95% CI -43 to -18) (moderate certainty of the evidence). Similarly, one of the RCTs, investigating time from symptom onset to imaging, detected a reduction in time, in favour of MSU (39 minutes difference in median, 95% CI IQR 26 to 52) (certainty of the evidence not graded). No statistically significant difference between groups in time from symptom onset to thrombolysis was detected (-50 mean minutes, 95% CI -117 to 18) (low certainty of the evidence). However, the effect direction of the two included RCTs investigating this outcome was the same, favouring MSU. Based on the evidence, in total, 11% more patients received thrombolysis with MSU care, compared to those who received conventional care (32% vs. 21%) (moderate certainty of the evidence). Among those who received thrombolysis, MSU patients were more than five times more likely (31% vs. 5.5%) to receive thrombolysis within 60 minutes (golden hour), than those who received conventional care (low certainty of the evidence). Furthermore, compared to conventional care, MSU care improved triage of patients with stroke to specialized hospitals (certainty of the evidence not graded), and increased the proportion of patients with 3-month modified Rankin Scale (mRS) score 0-3 (low certainty of the evidence). The mRS scale is used to measure physical function and runs from 0 to 6 (0 = no symptoms of disability, 6 = dead). No differences in 90-day mortality (RR 1.35, 95% CI 0.84 to 2.15) (low certainty of the evidence) or hemorrhagic complications (RR 0.55, 95% CI 0.23 to 1.34) (certainty of the evidence not graded) were detected. Radiation exposure for MSU staff or the public did not exceed established dose limits. We were not able to identify studies investigating the effectiveness of CT scanners localized in decentralized CT stations outside hospitals, or the use of prehospital CT in suspected severe head injuries. Health economic evaluation: The estimated annual cost of one MSU is approximately 6.4 million Norwegian kroner, and includes both daily operation- and depreciation costs on the investment. The health economic model simulation resulted in a quality-adjusted life-year (QALY) gain of 0.3 per patient who received thrombolysis through MSU care compared with conventional care. We calculated an absolute shortfall of 5.5 QALYs. We found that the expected cost per QALY is about 385,000 Norwegian kroner or lower if one MSU successfully reaches at least 35-40% (145-171) of thrombolysis patients per year. We assume that efficacy results are transferable to metropolitan areas in Norway. Our one-way sensitivity analyses indicate that the required patient proportion to achieve an incremental cost-effectiveness ratio (ICER) of 385,000 Norwegian kroner would decrease when the MSU costs decrease and increase when the MSU costs increase. Compared with conventional care of acute stroke, MSU care probably reduces the time from a patient’s first contact with the emergency dispatch center to thrombolysis, and increases the number of patients who receive thrombolysis. It may also lead to reduced time from a patient’s first contact with the emergency dispatch center to CT imaging, and to better functionality at 3 months after stroke (mRS score 0-3). We found an absolute shortfall of 5.5 QALYs for ischemic stroke patients, and that the expected cost per QALY is about 385,000 Norwegian kroner or lower if one MSU successfully reaches at least 35-40% (145-171) of thrombolysis patients per year. Decision makers must consider whether they think it is plausible that a minimum of 35-40% of patients could receive the intervention. Due to the lack of evidence, the effectiveness of decentralized CT stations outside hospitals and of prehospital CT in suspected severe head injuries is unknown.

Authors' methods: Clinical effectiveness and safety: In absence of eligible systematic reviews and HTAs, we conducted systematic searches for primary studies in a selection of relevant databases and trials registries. We limited the searches to publication year 2010 to present, but no restrictions to study type were applied. Two reviewers independently screened identified references, selected full-text publications that met predefined inclusion criteria, and critically appraised the included studies. Data extraction was performed by one reviewer, and checked by a second reviewer. For four outcomes, we were able to synthesize the findings by means of meta-analyses. For other outcomes, results were presented in tables and text. We assessed the certainty of the evidence for the main clinical outcomes using the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation). In GRADE, the certainty of the evidence is expressed either as high, moderate, low, or very low, depending on the level of confidence we have in the effect estimates. Health economic evaluation: We conducted a cost- and threshold analysis, which attempts to elucidate mean incremental cost-effectiveness ratios (ICERs) at different values for proportions of ischemic stroke patients receiving thrombolysis through mobile stroke unit (MSU) care compared to conventional care (use of standard ambulance). This method makes it possible to identify a threshold value for the proportion that is required for the MSU to achieve an ICER of a predefined level. We also calculated absolute shortfall for patients with acute ischemic stroke receiving conventional care in order to classify severity for the relevant patient population. Further, we performed a one-way sensitivity analysis to investigate the impact of the MSU cost parameter. We modified an existing probabilistic Markov decision analytic model for ischemic stroke patients, developed as a part of an HTA on mechanical thrombectomy conducted by the Norwegian Institute of Public Health in 2016. The analyses do not evaluate consequences of introducing MSUs in non-metropolitan parts of Norway, and they do not account for patients with other indications who might benefit from MSU care.

Project Status: Completed

Year Published: 2019

URL for published report: https://www.fhi.no/en/publ/2019/Prehospital-CT-for-early-diagnosis-and-treatment-of-suspected-acute-stroke-or-severe-head-injury/

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: Norway

Organisation Name: Norwegian Institute of Public Health

Contact Address: P.O. Box 222 Skoyen, N-0123, Oslo