NT-proANP and NT-proBNP for the diagnosis of stroke

Abstract

The present invention relates to a method for diagnosing a transitory ischemic attack (TIA) in a subject who is suspected to have exhibited a transitory ischemic attack, but who did not exhibit a stroke. The method is based on the determination of the amount of NT-proANP in a sample from said subject. Moreover, the present invention is directed to a method for diagnosing an acute cerebral ischemic event in a subject based on the determination of the amounts of NT-proBNP and NT-proANP in a sample from a subject. The method further comprises the step of calculating a ratio of the amounts of NT-proBNP and NT-proANP. Further envisaged by the present invention are kits and devices adapted to carry out the method of the present invention.

Claims

1. A method for diagnosing an acute cerebral ischemic event in a subject who is suspected to suffer from an acute cerebral ischemic event, comprising: determining the amount of NT-proANP in a blood, serum or plasma sample from said subject; determining the amount of NT-proBNP in a sample from said subject; calculating a ratio of the amounts of NT-proANP and NT-proBNP; comparing the calculated ratio to a reference ratio, thereby diagnosing the acute cerebral ischemic event based on the comparison of the calculated ratio to a reference ratio; wherein the reference ratio is derived from a sample from a subject known to have exhibited an acute cerebral ischemic event, wherein a ratio of NT-proANP to NT-proBNP in the sample from the test subject which is essentially identical to the reference ratio or which is larger than the reference ratio indicates that the subject has exhibited an acute cerebral ischemic event, and/or the reference ratio is derived from a sample from a subject known not to have exhibited an acute cerebral ischemic event, and wherein a ratio of NT-proANP to NT-proBNP in the sample from the test subject which is essentially identical to the reference ratio or which is lower than the reference ratio indicates that the subject has not exhibited an acute cerebral ischemic event; and treating a patient diagnosed with acute cerebral ischemic event with aspirin, heparin, stenting, anticoagulation therapy, anti-platelet therapy, and/or endarterectomy.

2. The method of claim 1 wherein the subject suffers from heart failure and/or from coronary artery disease.

3. The method of claim 1, wherein the subject who is suspected to have exhibited an acute cerebral event has shown symptoms of an acute cerebral event within 72 hours before the sample has been obtained.

4. The method of claim 1, wherein the subject who is suspected to have exhibited an acute cerebral event has shown symptoms of an acute cerebral event within 24 hours before the sample has been obtained.

5. The method of claim 1, wherein the sample has been obtained later than 1 one hour after the onset of symptoms of the acute cerebral event.

Description

(1) Example 1: Determination of NT-proBNP and NT-proANP

(2) NT-proBNP was determined using Roche's electrochemiluminescence ELISA sandwich test Elecsys proBNP II STAT (Short Turn Around Time) assay. The test employs two monoclonal antibodies which recognize epitopes located in the N-terminal part (1-76) of proBNP (1-108).

(3) NT-proANP (amino acids 1 to 98 of the pre-proANP peptide) was determined using the NT-proANP assay from Biomedica Medizinprodukte GmbH (Vienna, Austria). The catalogue number. BI-20892. The detection limit is 0.05 nmol/l. The assay makes use of polyclonal sheep anti proANP antibodies.

(4) The level of the biomarkers were tested in serum samples from the following group of subjects healthy subjects (n=149) patients with stable coronary artery disease CAD (i.e. patients in whom frequently stroke develops, n=235), patients with cardiac decompensation (n=64), patients with TIA (n=79). patients with minor and major stroke (n=61 and 108, respectively)
CAD Patients:

(5) A total of 235 patients with chronic artery disease were included into the study, mean age 64 years, they were 141 males and 94 females. In all patients, coronary artery disease was verified by angiography. A 50% reduction in vessel diameter was used for classification of 1, 2 or 3 vessel disease. Cardiac function was assessed by echocardiography and determination of NT-pro BNP

(6) Heart Failure:

(7) A further group of 64 patients has decompensated heart failure (24 women and 40 men, mean age 69 years). They were characterized by increasing shortness of breath in the previous 2 weeks, all patients could be classified as NYHA III or IV according to the NYHA classification.

(8) Healthy Controls:

(9) 149 clinically healthy human subjects were included into the study as controls, 52 males and 97 females (median age 41 years, range 19 to 56 years). These subjects had no cardiac disease as assessed by medical history and an electrocardiogram, no diabetes mellitus and no risk factors of these diseases. Moreover they had normal kidney function as assessed by normal creatinine values and malignant disorder.

(10) Stroke/TIA Patients:

(11) A total of 255 patients with TIA or ischemic stroke (mean age 70 years) were included in this study. Transitory ischemic attack was present in 23 patients, minor stroke was diagnosed in 61 patients and major stroke was found in 108 patients. In addition as described above caotoid and transcranial ultrasound as well as electro- and echocardiography were performed and the patients were classified according to the TOAST criteria. In patients with stroke and TIA, the biomarkers NT-proANP and NT-proBNP were measured in samples obtained at presentation as well as in samples obtained six and 24 hours after presentation. The median interval between the onset of symptoms and admission was 4.2 hours (25th percentile: 2.5, 75th percentile: 8 hours).

(12) Example 2: Results

(13) The following results were obtained (indicated are the Median levels, as well as the 25.sup.th and 75.sup.th percentile):

(14) TABLE-US-00001 NT-pro BNP NT-pro ANP pg/ml pg/ml Healthy subjects 37 882 N = 149 18-68 635-1280 Patients with stable CAD 266 2710 N = 236 95-928 1880-4662 Patients with Cardiac 4477 33600 Decompensation N = 64 1971-7131 12570-57800 TIA: n = 27 331 106000 165-473 79000-149000 Minor stroke n = 60 238 81000 79-547 43400-125000 Major stroke (n = 108) 412 107151 127-1053 70600-240000

(15) The surprising finding indicated that NT-proANP levels in stroke were significantly increased in patients with TIA and stroke. In particular, they were higher than in overt cardiac decompensation. Thus, NT-proANP separated cardiac patients from stroke patients. The determination of NT-proBNP provides additional information.

(16) Moreover, the ratios of NT-proANP to NT-proBNP were determined:

(17) The ratios were as follows (Median, 25th percentile/75th percentile):

(18) TABLE-US-00002 Healthy 74 (14/125) CAD 10 (4/25) Decompensated HF 10 (4/18) Major stroke 249 (128/603) Minor stroke 321 (149/670) TIA 524 (204/905)

(19) As it can be seen from the table, the determination of the ratio is advantageous since it allows for the differentiating between i) patients having risk factors of stroke/TIA, i.e. patients with coronary artery disease (CAD) and patients with heart failure (HF) which have high levels of NT-proANP and NT-proBNP, and ii) patients who have suffered from stroke or TIA.

(20) When NT-proANP values were followed in the course of stroke, the following values were obtained:

(21) TABLE-US-00003 NT-pro ANP pg/ml At presentation 106000 79000-149000 At 6 hours 95500 54000-139000 At 24 hours 82000 48000-139000

(22) Follow up indicated that this was a lasting effect, indicating that also past events could be recognized.

(23) Conclusions:

(24) The recognition of TIA is important as it may precede stroke which is frequently disabling. Frequently TIA lasts only for minutes and most TIAs resolve within one hour without causing permanent damage to the brain. The diagnosis of TIA is difficult as i) TIA mimics a variety other disorders depending on the localisation of TIA and as ii) the patient presents for assessment symptoms are no longer present which makes the final diagnosis difficult. TIA frequently develops in patients with pre-existing heart diseases such as systemic hypertension, coronary artery disease and heart failure of different origin. A surprising finding of this study was that NT-proANP which is known to be released in heart failure is highly elevated in stroke and surprisingly also in TIA even exceeds the levels found in patients with advanced and decompensated heart failure. Also the ratio of NT-proANP/NT-pro BNP can be safely used for this purpose, in particular in heart failure patients.

(25) The clinical importance of confirmation of suspected TIA lies in the identification of the underlying cause (e.g. cardioembolic), the appropriate intervention (angioplasty e.g. in carotis stenosis, anticoagulation in atrial fibrillation) and, thus, in the prevention of stroke and specifically major stroke.

(26) Moreover, it has been shown that the determination of the ratio of NT-proANP/NT-pro BNP allows for a reliable diagnosis of stroke and TIA, in particular in patients suffering from heart failure.