By Denise Uettwiller-Geiger, Ph.D., DLM (ASCP)

The economics of cardiac troponin testing
Physicians and laboratorians are often taxed to the limit of their abilities when it comes to properly categorizing chest-pain patients. The many variables and atypical presentation of cases can lead to wrong or delayed decisions, or in a worst-case outcome, to increased morbidity or even loss of life.

Denise Uettwiller-Geiger, Ph.D., DLM(ASCP), in her lab at John T. Mather Memorial Hospital.

In addition to poor clinical outcomes, the adverse financial consequences of inaccurate cardiac-related diagnoses can be formidable. For example, a myocardial infarction (MI) that is overlooked or misdiagnosed as a more benign condition can lead to malpractice suits. On the other hand, treating non-cardiac patients as if they were cardiac patients unnecessarily escalates costs.

Cardiovascular disease (CVD), with MI as the most common cause of death, is the most prevalent health challenge in the industrialized world. Fortunately, technology in the form of cardiac markers, espcially the cardiac troponin I (cTnI) assay, has emerged to help clinicians make faster and far more accurate diagnoses. Financial analyses indicate that the leading cTnI assays — for instance, the Access AccuTnI assay used at John T. Mather Memorial Hospital in Port Jefferson, N.Y. — have the potential to save a typical hospital nearly $900,000 per year.

The human and monetary costs of misdiagnosed chest pain
Some 8 million people a year visit U.S. hospital emergency departments (EDs) complaining of chest pain, according to the National Academy of Clinical Biochemistry (NACB). One million are found to have suffered an acute myocardial infarction (AMI) with another 1.2 million experiencing unstable angina (UA).

Diagnostic hurdles compound the pressure created by the large number of cases. The traditional biomarker creatine kinase (CK), the mostly cardiac-specific isoform CK-MB and other biomarkers are present in non-cardiac tissues such as skeletal muscles and, consequently, may yield false-positive results when used to test for cardiac damage. In addition, some patients — older women, in particular — may not have sufficient muscle mass for CK to produce meaningful results.

These and other issues make accurate diagnoses of chest-pain patients problematic, and hospitals often face two major consequences: unnecessary admissions and inappropriate discharges. Each of these can profoundly affect hospital finances.

First, of the 8 million chest pain patients who come to hospital EDs each year, 5 million are admitted with suspected cardiac disease. Yet half, or 2.5 million, of those admissions will prove unnecessary. The academy estimates that hospitals nationally overspend from $10 billion to $13 billion annually on excess admissions for chest pain.

But among the remaining 3 million patients who are discharged from the ED as non-cardiac cases, studies show that 2 to 13% have also been misdiagnosed. According to numerous sources, more malpractice lawsuits are filed against ED physicians for inappropriate discharge of AMI patients than for any other reason.

A biomarker that helps reduce costs
Improving the precision and speed of cardiac diagnoses means improving patient care and cost control. Experience and research have shown cTnI assays to be a key to achieving these two benefits. These benefits accrue from both the specificity and the sensitivity of the assays.

Because cTnI exists only in cardiac tissue, its presence in the blood is a more specific and definitive indicator of cardiac necrosis (death of cardiac tissue) than other markers. Though commonly used, CK and CK-MB biomarkers can produce false positives in patients with damaged skeletal muscle, renal failure, trauma or kidney damage.

And Troponin assays, as a class, demonstrate greater sensitivity to minimal myocardial damage (MMD) than other biomarkers. Indeed, the sensitivity of troponin assays led a joint committee of the European Society of Cardiology (ESC) and the American College of Cardiology (ACC) to redefine myocardial infarction (MI) in 2000. The committee’s document stated that MI was the appropriate diagnosis when any degree of myocardial necrosis had occurred, as indicated by even slight elevations of troponin levels in the blood. Thus, the sensitivity of troponin assays provides cost-effective protection against inappropriate discharges of chest-pain patients. At J.T. Mather, we use the Beckman Coulter Access AccuTnI assay, one of the most sensitive cTnI assays currently available.

Another important performance characteristic of this assay is its ability to bind to the stable portion of the troponin molecule, enabling it to detect cTnI in the blood even when the protein is in a degraded state. Following cardiac necrosis, troponin disintegrates rapidly after its release into the blood. Unlike many other assays, the Access AccuTnI assay targets the stable portion of the molecule. As a result, we are able to detect cardiac pathology that other assays may miss, particularly in late-presenting cases.

Finally, some assays yield false-positive results if interferences — such as heterophilic antibodies, HAMA and rheumatoid factor — are present in the blood. The assay in use at J.T. Mather has virtually eliminated problems from these potential interferences.

Laboratory administrators can use an economic model developed by bio-statistician Robert Parson, M.S., of Beckman Coulter, for a quantitative estimate of potential savings from utilizing cTnI assays in their own institutions. Using prior studies and including figures from a 1999 NACB document, the model predicts that utilizing cTnI assays in the triage of chest pain can decrease annual length of stay (LOS) by more than 8 percent. Associated annual cost reductions in the CCU and chest pain unit total more than 7 percent.

With 5,000 chest pain patients seen in the typical ED, institutions can realize an annual reduction of roughly 80 patient days in the CCU. Based on assumed costs of $4,000 per day, the annual net savings add up to $312,000.

Potential savings in chest pain units are even more dramatic. Parson calculates an annual aggregate reduction in LOS of 234 days. With estimated costs of $2,500 per day in this unit, annual net savings come to more than $585,000. The total annual net savings to an institution are more than $897,000. (Net savings in all cases above are based on the costs of the Access AccuTnI assay.)

Financial implications for a new category of patients
The diagnostic capabilities of troponin assays continue to evolve, and the NACB as well as a joint committee of the ESC and ACC have both issued recent recommendations for cardiac troponin level cutoffs.

For the Access AccuTnI assay, the 97.5th percentile URL of normal is 0.03 ng/mL, while the 99th percentile URL is 0.04 ng/mL. The recommended diagnostic cutoff value for AMI is 0.50 ng/mL. Thus Troponin I assays help clinicians to more accurately diagnose chest-pain patients and intervene with treatment and/or lifestyle education. Along with the obvious benefits for patients, institutions may reduce inappropriate discharges and avoid liability issues.

Over the long term, cTnI assays hold promise for making a positive impact on disease management, a strategy that employs early intervention and patients’ participation in maintaining their own health.The goals of disease management include improved patient outcomes, greater patient satisfaction, and cost reduction. The sensitivity and specificity of cTnI assays make them a valuable tool toward achieving these goals.

Denise Uettwiller-Geiger, Ph.D., DLM(ASCP), is the administrative director and a clinical chemist for the clinical laboratories at John T. Mather Memorial Hospital in Port Jefferson, N.Y.