Spontaneous Subarachnoid Hemorrhage: A Systematic Review and Meta‐analysis Describing the Diagnostic Accuracy of History, Physical Examination, Imaging, and Lumbar Puncture With an Exploration of Test Thresholds

Abstract

Background Spontaneous subarachnoid hemorrhage (SAH) is a rare, but serious etiology of headache. The diagnosis of SAH is especially challenging in alert, neurologically intact patients, as missed or delayed diagnosis can be catastrophic. Objectives To perform a diagnostic accuracy systematic review and meta-analysis of history, physical examination, cerebrospinal fluid (CSF) tests, computed tomography (CT), and clinical decision rules for spontaneous SAH. A secondary objective was to delineate probability of disease thresholds for imaging and lumbar puncture (LP). Methods PUBMED, EMBASE, SCOPUS, and research meeting abstracts were searched up to June 2015 for studies of emergency department (ED) patients with acute headache clinically concerning for spontaneous SAH. QUADAS-2 was used to assess study quality and, when appropriate, meta-analysis was conducted using random effects models. Outcomes were sensitivity, specificity, positive (LR+) and negative (LR−) likelihood ratios. To identify test- and treatment-thresholds, we employed the Pauker-Kassirer method with Bernstein test-indication curves using the summary estimates of diagnostic accuracy. Results A total of 5,022 publications were identified, of which 122 underwent full text-review; 22 studies were included (average SAH prevalence 7.5%). Diagnostic studies differed in assessment of history and physical exam findings, CT technology, analytical techniques used to identify xanthochromia, and criterion standards for SAH. Study quality by QUADAS-2 was variable; however, most had a relatively low-risk of biases. A history of neck pain (LR+ 4.1 [95% CI 2.2-7.6]) and neck stiffness on physical exam (LR+ 6.6 [4.0-11.0]) were the individual findings most strongly associated with SAH. Combinations of findings may rule out SAH, yet promising clinical decision rules await external validation. Non-contrast cranial CT within 6 hours of headache onset accurately ruled-in (LR+ 230 [6-8700]) and ruled-out SAH (LR− 0.01 [0-0.04]); CT beyond 6 hours had a LR− of 0.07 [0.01-0.61]. CSF analyses had lower diagnostic accuracy, whether using red blood cell (RBC) count or xanthochromia. At a threshold RBC count of 1,000 × 106/L, the LR+ was 5.7 [1.4-23] and LR− 0.21 [0.03-1.7]. Using the pooled estimates of diagnostic accuracy and testing risks and benefits, we estimate LP only benefits CT negative patients when the pre-LP probability of SAH is on the order of 5%, which corresponds to a pre-CT probability greater than 20%. Conclusions Less than one in ten headache patients concerning for SAH are ultimately diagnosed with SAH in recent studies. While certain symptoms and signs increase or decrease the likelihood of SAH, no single characteristic is sufficient to rule-in or rule-out SAH. Within 6 hours of symptom onset, non-contrast cranial CT is highly accurate, while a negative CT beyond 6 hours substantially reduces the likelihood of SAH. LP appears to benefit relatively few patients within a narrow pre-test probability range. With improvements in CT technology and an e...

ACR Appropriateness Criteria® Headache

“…CT Head. The most appropriate initial imaging test in this clinical setting is a noncontrast head CT [31][32][33]. Negative predictive value of CT, when performed with modern scanners within the first 6 hours of symptoms and interpreted by a staff radiologist, might be as high as 99.9% [33,34].…”

What is Currently the Best Investigational Approach to the Patient With Sudden‐Onset Severe Headache?

“…In general, they found that pre-CT likelihood of SAH must be above 20% if patients were likely to benefit from a LP. 6 In other words, a normal noncontrast cranial CT within 6 hours of thunderclapheadache onset makes supplemental investigation with LP or CTA redundant, provided that the pretest probability for SAH is not too high. A validation study of Blok and colleagues supported this.…”

“…Thunderclap headache, hyper acute headache reaching its pain maximum within 1 minute, is the cardinal feature of SAH, but not very specific -about half of the patients with SAH experience this, but only 1 in 10 with thunderclap headache has actually bled. 6 Different clinical tools to rule out SAH have been developed. Table 1 shows the most important causes.…”

Validation of the Ottawa Subarachnoid Hemorrhage Rule in patients with acute headache

“…6,7 However, a population-based study involving patients admitted to hospital through emergency departments in Ontario with a most responsible diagnosis of nontraumatic subarachnoid hemorrhage found that over 5% of confirmed subarachnoid hemorrhages were missed at initial presentation, especially in smaller hospitals. 8 Therefore, identifying which patients with headache require investigations to rule out this catastrophic diagnosis, and which do not, is a critical decision in emergency medicine.…”