What are the assay methods for brain natriuretic peptide (BNP)?

Updated: Jan 08, 2018
  • Author: Donald Schreiber, MD, CM; Chief Editor: Erik D Schraga, MD  more...
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Answer

Answer

First-generation assays for brain natriuretic peptide (BNP) were competitive radioimmunoassays that required extraction and purification of the plasma sample. Second-generation assays were based on monoclonal antibodies and radioisotope labels. These assays provided improved sensitivity and precision. Commercial versions of the monoclonal antibody assay first appeared in 1994 and initially required 12-36 hours to complete.

Third-generation assays, which provided results in as little as 15 minutes, became available in 2000. These rapid assays used immunofluorescent methods. All of the assays for BNP and NT-proBNP that are commercially available for clinical use in the United States are rapid immunoassays.

The assay used in the Breathing Not Properly study, which first suggested clinically useful BNP cutoff values for diagnosing acute congestive heart failure (CHF), was the point-of-care Triage BNP Test (Biosite Diagnostics Inc; San Diego, CA). Other manufacturers also market rapid-turnaround BNP assays, including the ADVIA Centaur BNP assay (Bayer HealthCare Diagnostics; Tarrytown, NY) and the AxSYM BNP assay (Abbott Diagnostics; Abbott Park, IL).

Assays for the NT-proBNP fragment became available in late 2002. The Elecsys NT-proBNP assay (Roche Diagnostics; Indianapolis, IN) was evaluated in the ProBNP Investigation of Dyspnea in the Emergency Department (PRIDE) study. Other NT-proBNP assays include the Dimension test and the Stratus CS Acute Care NT-proBNP assays (Dade Behring Inc; Deerfield, IL).

Result considerations

When the literature or laboratory data from other institutions are evaluated, care must be taken not to extrapolate the results of one assay to another. Assay values for NT-proBNP have performance characteristics that are different from those for BNP, and evidence-based, rule-in and rule-out CHF cutoff levels change depending on the type of assay used.

Equally important is that the performance characteristics of these tests vary with the patients to whom they are applied; a negative result in a population with a low pretest probability of CHF has an increased negative predictive value. Finally, assays from various manufacturers differ slightly in their performance characteristics. Physicians must be familiar with the particular assay available at their facility.


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