Die Kurzzeitstabilität von BNP und NTproBNP in der Präanalytik

OBJECTIVES: It is known that B-type natriuretic peptide (BNP) and N-terminal proBNP (NTproBNP) are useful predictors of heart failure and left ventricular dysfunction. BNP even has a sensitivity of 88% for the diagnosis of left ventricular hypertrophy and a negative predictive value of 97%. Furthermore, in vitro, NTproBNP is more stable than BNP over 48 hours. Yet, nothing has been reported about the short-term stability (0 min. up to 24 hours after blood taking) of the two peptides. This is important since in most cases the blood cannot be examined in a laboratory right after taking it. METHODS: Blood was taken from 24 volunteers (four healthy, six heart failure patients, three ICU patients and eleven Patients with chronic hemodialysis) into six EDTA-, two heparin-tubes, and one serum-tube. The EDTA-tubes were handled as follows: two enclosed Trasylol®, two were left as whole blood, and two were centrifuged to plasma. Half of the samples were stored at 4°C and half of them including the serum were stored at room temperature. For three volunteers a glass tube was also used and stored at room temperature. Then the BNP and NTproBNP levels were measured right away (0 min.), after 15 min., after 30 min., after one hour, after two, after four, after six, after twelve and after 24 hours. For measuring, the ADVIA Centaur, Bayer, (BNP) and the Elecsys 2010, Roche, (NTproBNP) were used. They are both working with a chemi-luminescence immuno assay. RESULTS: NTproBNP is much more stable than BNP over 24 hours - no matter wich blood taking tube is used. BNP was the most stable in EDTA-tubes either stored at 4°C or at room temperature. The additional Aprotinin had no detectable effect on the stabilization. The heparin-, the serum-, and the glass tubes showed a rapid decrease of BNP. Comparing BNP and NTproBNP, the second was more stable in all tubes during the measured 24 hours and even increased slightly. There was no difference between storage at 4°C and room temperature for both BNP and NTproBNP. CONCLUSION: Regarding the short term stability of BNP and NTproBNP, blood should be taken with EDTA-tubes and should be stored as plasma or whole blood before measuring. Plastic tubes should be used instead of glass tubes. This way a reliable diagnosis with BNP or NTproBNP can be ensured.