Screening patients with a family history of subarachnoid haemorrhage for intracranial aneurysms: screening uptake, patient characteristics and outcome
- Division of Clinical Neurosciences, University of Edinburgh, Western General Hospital, Edinburgh, UK
- Correspondence to Dr R Al-Shahi Salman, Division of Clinical Neurosciences, University of Edinburgh, Western General Hospital, Crewe Rd, Edinburgh EH4 2XU, UK;
Contributors TDM collected and analysed the data and wrote the manuscript. RA-SS analysed and the data and wrote the manuscript. All authors were involved in the project design.
- Received 21 June 2011
- Accepted 17 July 2011
- Published Online First 23 September 2011
Background and purpose People with one or more first degree relative affected (FDRA) by aneurysmal subarachnoid haemorrhage (aSAH) are at a higher lifetime risk of an aSAH than those without a family history. Screening may be worthwhile for people with two or more FDRA by aSAH. Little is known about the characteristics of people with a family history of aSAH who undergo screening in clinical practice.
Methods Observational analysis of consecutive attendances at an intracranial aneurysm screening clinic.
Results Of 96 adults seen, 19 did not have a family history of aSAH and 77 had one or more FDRA by aSAH: 35 had two or more FDRA, 21 had one FDRA plus one or more affected second degree relative and 21 had one FDRA only. In these three respective groups, 29 (83%), 15 (71%) and five (24%) adults underwent screening, of whom six (21%), two (13%) and one (20%) had an aneurysm detected (p=0.5). Of the nine patients with aneurysms, four underwent treatment. Considering other risk factors, adults with two or more FDRA were more likely to be hypertensive (OR 3.3, 95% CI 1.0 to 10.8; p=0.046) but were no more likely to smoke or drink to excess than adults with one FDRA. Adults who underwent screening were more likely to be hypertensive and drink alcohol to excess (both p=0.03), but were no more likely to smoke than those who were not screened.
Conclusions In clinical practice, people undergoing intracranial aneurysm screening had stronger family histories of aSAH and they were also more likely to have modifiable risk factors for aSAH.
The point prevalence of unruptured intracranial aneurysms in the adult population is ∼2% but the point prevalence is ∼4% in people with one or more first degree relative affected (FDRA) by aneurysmal subarachnoid haemorrhage (aSAH) and ∼8% in those with two or more FDRA by aSAH.1 There is a small increase in the lifetime risk of aSAH for people with one or more FDRA by aSAH compared with people without a family history.1 2 In particular, the best available estimate of the lifetime risk of aSAH for people with two or more FDRA by aSAH is ∼26%,3 so screening may be worthwhile for people with two or more FDRA by aSAH for whom it is generally recommended.4 However, the treatment of unruptured intracranial aneurysms can be risky and is not supported by randomised controlled trials. Furthermore, randomised controlled trials have not been performed to investigate the overall effectiveness of intracranial aneurysm screening programmes, which may have benefits (eg, reassurance or prevention of aSAH) as well as potentially harmful consequences (eg, radiation exposure during investigation, false reassurance from a normal screening test, impaired quality of life from living with an untreated unruptured intracranial aneurysm or adverse effects of the treatment).5 6
Therefore, we sought to evaluate the screening uptake, patient characteristics and outcome of our intracranial aneurysm screening service for people with a family history of aSAH, which recommends referral of adults with two or more FDRA by aSAH, or one FDRA and one or more affected second degree relative.
Patients and methods
We performed a retrospective, observational analysis of consecutive attendances at an intracranial aneurysm screening clinic at the Western General Hospital, Edinburgh, UK, from October 2006 to June 2009 inclusive. Referrals came predominantly from primary care with a few from secondary care (eg, nephrologists referring adults with autosomal dominant polycystic kidney disease with a family history of aSAH). In clinic, a consultant (RASS, RJD or PMW) reviewed the medical histories of the attendees, family history and modifiable risk factors for aSAH, and discussed the pros and cons of screening with each attendee, who made the final decision about whether or not to proceed with screening.
One author (TDM) collected data from clinic letters and case notes on non-modifiable risk factors (age, sex, and number of first, second or third degree relatives affected by aSAH), modifiable factors (smoking history, alcohol consumption—dichotomising into more or less than 14 units/week (women) and 21 units/week (men)7 8—and hypertension (on antihypertensive therapy or blood pressure ≥160/100 mm Hg)),9 whether a screening test was undertaken, whether an intracranial aneurysm was detected and whether a detected aneurysm was treated.
We compared the characteristics of patients with only one FDRA with those with two or more FDRA, as well as patients who were screened with those who were not screened. We used non-parametric statistics for continuous descriptors (medians) and their comparison (Mann–Whitney U test). We used χ2 statistics (or Fisher's exact test, where appropriate) and ORs (and 95% CIs) for comparing categorical data.
Of 97 adults who attended the aneurysm screening clinic, detailed family history taking confirmed that 77 adults had one or more FDRA: 35 had two or more FDRA, 21 had one FDRA plus one or more affected second degree relative and 21 had one FDRA only (figure 1). Therefore, 56 patients (73% of patients with a family history of aSAH and 58% of all patients) met the strict recommended referral criteria for the clinic. Adults with two or more FDRA were older and more likely to be hypertensive than adults with just one FDRA, but were no more likely to smoke or drink alcohol to excess (table 1). Patients with stronger family histories were more likely to proceed to screening with CT angiography, although there was no statistically significant relationship between the strength of family history and likelihood of detecting an aneurysm in adults who underwent screening (table 1). Adults who underwent screening were more likely to be hypertensive and drink alcohol to excess than those who were not screened (table 1).
Among the 49 adults who underwent screening, 10 unruptured intracranial aneurysms were detected in nine adults (18% of those screened). Six of these aneurysms were in the anterior circulation. The remaining four aneurysms were in the posterior circulation, three of which were detected in patients with two or more FDRA. Four (44%) of these nine adults underwent elective aneurysm treatment: two adults with a posterior circulation aneurysm and a family history of two or more FDRA, and two adults with one FDRA (one of whom had an anterior circulation aneurysm and the other had a posterior circulation aneurysm). One patient underwent emergency aneurysm treatment following an aSAH only a few days after the screening test had detected the aneurysm in its unruptured state. The other unruptured aneurysms were not treated because the risks of treatment were judged to outweigh the risk of leaving them untreated.
In a specialist intracranial aneurysm screening clinic, fewer than half of the patients referred were confirmed to have two or more FDRA by aSAH after detailed family history taking. We found that people with two or more FDRA by aSAH were older (in keeping with the natural history of aneurysm development) and more likely to be hypertensive than those with just one FDRA. Unsurprisingly, those who underwent screening had stronger family histories but were also more likely to be hypertensive and drink alcohol to excess. An intracranial aneurysm was detected in almost one-fifth of those screened: in this small sample, this proportion did not vary according to the strength of the family history. Fewer than half of the people with detected unruptured aneurysms were treated.
Modifiable risk factors, including alcohol consumption >300 g/week (37.5 units of alcohol per week), hypertension and smoking each account for ∼20% of the population attributable risk for aSAH whereas a family history of one or more FDRA accounts for 11%.10 This practice based evaluation demonstrates how some modifiable risk factors are more prevalent in those with stronger family histories, and especially in people who elect to undergo screening. Both the strength of the family history as well as the existence of modifiable risk factors may influence patients considering screening as well as the doctors who advise them.5 Screening might benefit these patients by detecting unruptured aneurysms and identifying those patients who may benefit from angiographic monitoring of aneurysm size, although fewer than half of the aneurysms detected were amenable to treatment. Conversely, screening might harm these patients either by a normal imaging study providing false reassurance (and diminishing the impetus to address modifiable risk factors) or by leaving them with an unruptured and untreated aneurysm and attendant psychological complications.11 12
This evaluation benefited from being set in everyday clinical practice and providing data on the associations between modifiable risk factors and patients' family histories and preferences for undergoing screening, although 10% of the people who were screened did not meet our referral criteria and 21% of the people who met our screening criteria declined screening (again reflecting the realities of clinical practice). The careful counselling of adults referred to the clinic, and identification of adults at risk of harbouring an intracranial aneurysm, appeared to select a group of adults with an aneurysm prevalence higher than the 2% population point prevalence. The study was sufficiently powered to detect some statistically significant associations—especially among the rare group of patients with two or more FDRA by aSAH3—but we cannot exclude the effects of chance. The generalisability of our findings could be assessed if similar data were published by other intracranial aneurysm screening clinics.
Our findings encourage attention to primary prevention of aSAH (and other cardiovascular diseases) by addressing modifiable risk factors both in people with a strong family history of aSAH and in those who seek screening for intracranial aneurysms.
We are grateful to Edith Wood, clinical nurse specialist in interventional neuroradiology, for her help with data collection.
Funding RA-SS was funded by a clinician scientist fellowship from the UK Medical Research Council.
Competing interests PW does consulting work for Micrus and Microvention who manufacture coils and other equipment used in aneurysm coiling.
Ethics approval This project met the UK National Research Ethics Service criteria for a service evaluation (http://www.nres.npsa.nhs.uk/applications/guidance/research-guidance/?entryid62=66984) and therefore did not require ethics approval.
Provenance and peer review Not commissioned; externally peer reviewed.