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March 2007
Feature Story

eGFR calculations

In the article “Good idea, bad law: requiring eGFR test” (January 2007) there is a sentence that says, “The main difficulty: The equation includes negative fractional exponents that are difficult for some computers to handle.” I learned in high school mathematics that q–y = 1/qy [a number q raised to the power –y is the inverse of the number q raised to the power y]. For the fractional exponent, take the log of the number, multiply by the fractional exponent, and determine the antilog. A computer capable of handling exponents would surely be capable of handling inverses and logs. If what is written is true, the problem is not with the computer systems but the loss of mathematical skills among pathologists. Todd & Sanford 15e contains a log table. Tietz 2e contains a section on laboratory mathematics, the first paragraph of which is exponents. There was a time in the recent past when technologists and pathologists had the reputation of thinking like scientists and mathematicians and expected themselves to do so. What is happening to us?

Gerald Wedemeyer, MD
UHC Laboratory

Clarksburg, WVa.

Send-out testing

I enjoyed the article on send-out testing (Related article: Simplifying send-outs—what experts advise, February 2007). I have experience as a user and provider of reference lab services and would like to add an opinion to the discussion.

The primary factors in selecting a reference lab should be quality and cost. Quality is often assumed, which is a mistake. The quality of a result varies from lab to lab. A lab test is not a commodity. Cost needs to be calculated as the aggregate cost to the health care system, not just the negotiated cost of the test. Aggregate cost includes the cost of poor quality.

For a test result to have value it must be timely, accurate, and clinically relevant. Timely means the result is available when and where the clinician needs it. Accurate means it can discriminate disease from non-disease, and treatment success from treatment failure. Clinical relevance means the physician has ordered the most useful test available to diagnose and treat the patient. The reference lab should be an asset in physician education.

For hospital inpatients a key benchmark of aggregate cost is length of stay. If waiting for lab results causes delays in patient care, the impact on aggregate cost will surely be more than the cost of the test. We in the lab need to ensure our administrators understand this. Budget restraints on the lab should not increase aggregate costs. Poor-quality patient care always increases costs.

When considering bringing a test in-house it is critical to maintain timeliness, accuracy, and clinical relevance. Results need to get to the clinician when needed, not when the lab has a cost-effective batch size. Accuracy is maintained with thorough test validation done by competent and well-trained staff. Regarding clinical relevance, the cheapest test is the one not done, and the most expensive is one that provides no clinical value but may produce unnecessary downstream costs. The reference lab’s test menu, as well as yours, should be based on what provides the best patient care, not the most “billables.”

Our clinicians and their patients deserve reliable test results. If during the RFP and site visit decision process for selecting a reference lab there are any concerns about quality, do not let test cost alone drive the decision. Robert Michel has said elsewhere that the leading category of claims for malpractice actions filed annually has been in recent years failure to diagnose. Malpractice suits filed with a claim of failure to diagnose certainly show that, in some cases, a laboratory may have contributed to an undesirable outcome because it provided incorrect test results or failed to respond to inappropriate test ordering, both of which the lab is accountable for. The CAP and Joint Commission say the laboratory director is accountable for selecting a reference lab based on quality and service. Accountability is not with finance, the group purchasing organization, or the administrator.

The contributors to your article made a number of useful points. To those I would add: The most expensive test is the one done or ordered incorrectly.

L. John Eckhart
Quality Coordinator

Division of Anatomic Pathology

Department of Laboratory

Medicine and Pathology

Mayo Clinic

Rochester, Minn.