CME ARTICLE The influence of anaemia on stroke prognosis and its relation to N-terminal pro-brain natriuretic peptide M. Nybo, S. R. Kristensen, H. Mickley and J. K. Jensen Department of Clinical Biochemistry, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark Keywords: anaemia, N-terminal pro-brain natriuretic peptide, prognostic, stroke Received 27 March 2006 Accepted 8 June 2006 Anaemia is a negative prognostic factor for patients with heart failure and impaired renal function, but its role in stroke patients is unknown. Furthermore, anaemia has been shown to influence the level of N-terminal pro-brain natriuretic peptide (NT- proBNP), but this is only investigated in patients with heart failure, not in stroke patients. Two-hundred-and-fifty consecutive, well-defined ischemic stroke patients were investigated. Mortality was recorded at 6 months follow-up. Anaemia was diagnosed in 37 patients (15%) in whom stroke severity was worse than in the non- anaemic group, whilst the prevalence of renal affection, smoking and heart failure was lower. At 6 months follow-up, 23 patients were dead, and anaemia had an odds ratio of 4.7 when adjusted for age, Scandinavian Stroke Scale and a combined variable of heart and/or renal failure and/or elevation of troponin T using logistic regression. The median NT-proBNP level in the anaemic group was significantly higher than in the non-anaemic group, and in a multivariate linear regression model, anaemia remained an independent predictor of NT-proBNP. Conclusively, anaemia was found to be a negative prognostic factor for ischemic stroke patients. Furthermore, anaemia influ- enced the NT-proBNP level in ischemic stroke patients, an important aspect when interpreting NT-proBNP in these patients. Introduction Ischemic stroke has numerous well-known risk factors [1], but the importance of anaemia as an independent risk factor has mainly been described in children [2]. In adults, increased stroke risk because of sickle cell anaemia is known [3], but anaemia in general is mostly casuistically described as a risk factor [4,5]. The few studies investigating low haematocrit as a risk factor of stroke have been conflicting [6–8] and generally focus has been on the impact of a high haematocrit because of the well-known consequences of hyperviscosity [9,10] Recently, anaemia has been reported independently associated with increased mortality in the elderly [11], and furthermore anaemia is an independent predictor of mortality in patients with heart failure [12–14] and impaired renal function [15]. This aspect has only been scarcely studied in ischemic stroke patients [16]. The hormone brain natriuretic peptide (BNP) is processed as a response to haemodynamic stress and local ischemia [17,18] and is mainly synthesized in cardiomyocytes in response to increased ventricular wall tension. Growing evidence indicates that ischemic stroke in itself raises the levels of BNP and its split product N-terminal proBNP (NT-proBNP) of un- known reasons [19–22]. Furthermore, NT-proBNP levels seem to provide prognostic information in stroke patients [23,24] However, several confounders are known, e.g. age, gender and kidney function [25,26], and recently anaemia has also been suggested to influ- ence the level of NT-proBNP [12,27,28]. Therefore, observational data on patients with acute ischemic stroke were collected with the following aims: 1 To investigate if anaemia may be of prognostic importance after ischemic stroke. 2 To describe the importance of haemoglobin as a confounder in measurement of NT-proBNP in the context of acute ischemic stroke. Methods Subjects Patients admitted to the Department of Neurology, Odense University Hospital, in the period August 2003– Correspondence: Dr Mads Nybo, Department of Clinical Biochemistry, Rigshospitalet, Copenhagen University Hospital, DK-2100 Copenhagen V, Denmark (tel.: +45 3545 5509; fax: +45 3545 4640; e-mail: mads.nybo@rh.hosp.dk). This is a Continuing Medical Education paper and can be found with corresponding questions on the Internet at: http://www. blackwellpublishing.com/products/journals/ene/mcqs. Certificates for correctly answering the questions will be issued by the EFNS. Ó 2006 EFNS 477 European Journal of Neurology 2007, 14: 477–482 doi:10.1111/j.1468-1331.2006.01591.x