A-026 False Elevation of Blood BNP in Patients with Acute Heart Failure Treated with Lyophilized Recombinant Human Brain Natriuretic Peptide Caused by Improper Blood Sampling: A Case Report

Abstract Background A 54-year-old male patient was diagnosed with acute myeloid leukemia complicated by pulmonary infection. Ten days after chemotherapy, the patient presented with bilateral pulmonary rales and NT-proBNP of 7180 pg/mL. Recombinant human brain natriuretic peptide (rhBNP) was initiated for treatment of suspected heart failure. B-type natriuretic peptide (BNP) levels were measured daily to monitor treatment efficacy. After decreasing steadily to normal range, the patient’s BNP level suddenly surged to 10072.4 pg/mL on the 10th day of rhBNP treatment. This contrasted with the patient*s clinical manifestations. However, when NT-proBNP was measured using Vitros 5600(QuidelOrtho), the result was 531 pg/mL, which clinicians deemed consistent with the patient*s clinical presentation. In this report, we present a case of falsely elevated BNP levels in heart failure after rhBNP treatment due to improper blood sampling. Methods Using BNP results of other samples collected on the same day, we confirmed there was no systematic deviation in the detection system (Abbott Architect I2000, chemiluminescence method). A quality check at the patient*s ward showed that the sample with abnormally high BNP was drawn from the micro-pump tube through which rhBNP was being infused. This was identified as a possible cause of falsely elevated BNP. Therefore, we examined the change in BNP and NT-proBNP levels from July 7th to July 11th on Vitros 5600 based on two blood samples from both the patient’s arms (non-infusion side and micro-pump tube). The patient*s last administration of rhBNP was on July 8th. We statistically analyzed the data of 244 clinical specimens tested for both BNP and NT-proBNP during the first half of 2023. Results Although NT-proBNP had dropped to the normal range after the patient*s acute heart failure was treated with rhBNP, BNP was still markedly higher than the upper limit of the normal level, particularly in the blood samples collected from the micro-pump tube. On July 7, the sample from the non-infusion side yielded a BNP of 674 pg/mL and NT-proBNP of 229 pg/mL. The sample from the micro-pump tube yielded a BNP over 25,000 pg/mL and NT-proBNP of 223 pg/mL. The following graph (Fig.1) shows the patient’s BNP and NT-proBNP test results from July 7th to July 11th, where NT-proBNP remained within the normal range (50∼75 years old <900 ng/L) throughout, while BNP dropped rapidly to the normal level after discontinuing rhBNP. In the analysis of 244 patients, 10 patients were undergoing rhBNP treatment when the blood samples were collected and had higher BNP than NT-proBNP in the first half of 2023. Conclusion Non-cardiologists lack a clear understanding of whether to select BNP or NT-proBNP for monitoring rhBNP treatment in acute heart failure patients. Given the significant difference in their values, randomly changing the detection index is detrimental to disease monitoring. When monitoring rhBNP treatment efficacy, blood collection from either infusion-side arm or non-infusion side arm will affect BNP test results, but not NT-proBNP. Nurses are unaware of the impact of rhBNP on BNP levels during the blood collection process. Falsely elevated BNP can potentially mislead clinician judgment.