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Letters to the Editor |
1 Division of Cardiology, Department of Medicine, Veteran’s Affairs Medical Center and University of California, San Diego, CA
aAddress correspondence to this author at: VAMC Cardiology 111-A, 3350 La Jolla Village Dr., San Diego, CA 92161. Fax 858-552-7490; e-mail amaisel{at}ucsd.edu.
To the Editor:
Point-of-care B-natriuretic peptide (BNP) assays have become an accepted part of the diagnostic armamentarium for the physician attending to acutely dyspneic patients (1). The present study was done to analyze the evolving use of BNP measurements in a variety of settings at the San Diego Veteran’s Affairs (VA) Hospital, the first US institution to implement the commercialized Triage BNP Assay (2).
The study was approved by the Institutional Review Board. An analysis of the total number of BNP assays and the departments from which the assays were ordered was performed on all BNP measurements performed at the San Diego VA Hospital during the months of January through March of 2001, 2002, and 2003. Because we compared the use of BNP testing in the same quarter of the year over the 3 consecutive years, we believed it would effectively show the trends in BNP assay use.
During the period January through March of 2001, there were 537 BNP assays run (Table 1
). Records were obtained from patient sample logs kept in the point-of-care laboratory at the San Diego VA Hospital. Of the 537 requests, 72% (n = 387) were ordered from the Emergency Department (ED), whereas only 11% (n = 59) were ordered from the Intensive Care Unit (ICU), 9% (n = 48) from inpatient departments, and 8% (n = 43) from outpatient departments. One year later, BNP orders rose to 1466, with only 27% from the ED. One-third (n = 542) came from outpatient departments, 20% (n = 293) from inpatient wards, and 16% (n = 235) from the ICU. By 2003, BNP assays performed grew to 2072, with the total assays ordered in the ED similar to previous years, although the percentage relative to all BNP assays decreased to 20% (n = 414). Although there was no decrease in the use of BNP in the ED, the relative percentage decreased as the use diversified in other clinical arenas. The overall number of BNP tests ordered from the ED remained the same over the years, perhaps because of saturation, i.e., almost everyone reporting to the ED with shortness of breath might have undergone BNP testing.
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The majority of BNP assays (47%) ordered in this last period were from the outpatient setting (n = 974). Although we could not segregate the outpatient use based on the origin of the BNP test request, i.e., whether the test was ordered by an internist and a cardiologist, the overall increase in outpatient use of BNP testing was likely to be evenly distributed between the two because the ordering of BNP tests by medical residents is a common practice at the VA Medical Center. The BNP assays ordered from ICU and inpatient wards amounted to 18% (n = 373) and 15% (n = 311), respectively. The distribution of assays by location changed significantly across years (
2 = 614.32; df = 6; P <0.001).
Over the past 3 years the large increase in BNP assays ordered has transcended use of the assays in the ED. Some of this increase has occurred in conjunction with a wealth of emerging clinical data describing biomarker-guided diagnostic, management, and risk stratification strategies (3). Much of this literature has discussed the many uses and information provided by obtaining and monitoring BNP concentrations in patients admitted to the hospital. BNP is the first biomarker that has found value in monitoring of patients, in tailoring management and titrating therapy (4), in providing objectivity in assessing discharge and admission criteria, and in predicting both adverse cardiac events and readmissions in congestive heart failure inpatients (5).
Interestingly, as clinicians learned to use BNP results in various clinical settings, it was in the outpatient setting that BNP test usage experienced the most growth in (8% in 2001 to 47% in 2003), accounting for the majority of assays ordered in the time period assessed in 2003. Although monitoring of BNP in the outpatient setting has not yet been shown effective in tailoring treatment of congestive heart failure, several large-scale studies are underway to test this hypothesis. The fact that effective treatments for heart failure have been correlated to decreasing BNP concentrations bodes well for future applications in tailoring treatment and in determining the overall stability of the patient outside the hospital (6). These results may also help delineate the appropriateness of the use of BNP testing in the outpatient setting and avoid any overuse that might occur. BNP concentrations have also been shown to be of value in several outpatient situations, including assessing volume overload and prognosis in renal failure (7), as well as in assessing the severity of valvular heart disease (8).
Acknowledgments
Dr. Maisel is a consultant for Biosite Inc., and has received research support from Biosite Inc., Roche, and Bayer Diagnostics
References
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