Quality Requirements and Standards
"The Truth, the Whole Truth, and Nothing but the Truth"
As we look at the quality of laboratory medicine, we need a demanding standard for judging the truth. See how some new tests (hs-CRP) and new recommendations (diabetes) fare when they're held up to the "the truth, the whole truth, and nothing but the truth" standard. (Preview)
A Demanding Standard for Quality:
- Clinical quality (usefulness) of a laboratory test
- The truth about hs-CRP
- Analytical quality (reliability) of a laboratory test
- The truth about glucose
- The truth about glycated hemoglobin
- The importance of "nothing but the truth"
An updated version of this essay appears on the Nothing but the Truth about Quality book.
I had an experience recently that gave me a new insight into quality. In studying certain evidence, it became clear that the evidence available, even if true, was not sufficient to know if it represented the truth. I suddenly understood the meaning of telling "the truth, the whole truth, and nothing but the truth".
Partial evidence may not be a lie, but it isn't necessarily the truth. To know the truth requires full disclosure of the available evidence (the whole truth), plus recognition of other factors that may confound the truth (nothing but the truth).
American politicians provide a good example of telling only part of the truth. There is always at least one fact to support their statements, but they seldom tell the whole truth and nothing but the truth. In the heat of political campaigns, one might wonder whether there is even one iota of truth (an infinitesimal amount).
As scientists, we think we're objective and never stray from the truth. Do you think our work measures up to the "truth standard?" Here are some examples where the truth standard challenges the quality of laboratory medicine.
In the evening news on January 27, 2003, Dan Rather talked about THE new test for heart disease and the recommendations for widespread use. Of course, this is the high sensitivity C- reactive protein test (hs-CRP) that has been growing and growing in interest through publications of more and more articles in scientific journals. Now the test has made it into main street journalism and will be covered in the "medical moments" discussions on local TV. The February 2003 issue of Medical Laboratory Observer shows an advertisement (Dr. Shuman shown here) and includes a product announcement for a new instrument that "is suited to screening of large patient populations in specific clinical locations." Pretty soon there will be advertisements telling you to "remind your doctor" about the importance of this new test to prevent future cardiac events.
In evaluating a new diagnostic test by the "truth standard", the test should demonstrate the following characteristics:
- First, a relationship to the disease of interest;
- Second, a reliable measurement process that provides correct test results; and
- Third, other factors should not interfere and confound the meaning of the test result.
The first dimension of truth has been demonstrated by epidemiological studies that show a relationship between slight elevations of CRP and a higher risk of future cardiovascular events. A risk assessment algorithm has been developed that makes use of a series of five clinical cutpoints, thereby the name "quintiles of risk".
The second dimension of truth is provided by special high sensitivity assays designed to measure very low concentrations of CRP. These assays are now being marketed and make it possible for routine service laboratories to provide the tests widely throughout the country.
The third dimension of truth is more difficult to assess. First of all, CRP will be elevated in many common infections, therefore the test is by its very nature expected to often provide high results due to any infectious process. That suggests that false positives will be a big problem when the test is used widely for screening individuals. Even if such infections were absent, the classification can be confounded by the biologic variation of the individual patient, as discussed in the January 2003 issue of clinical chemistry [1,2]. I also assert that the test cannot be adequately controlled to meet the demanding analytical requirements of the quintile classification scheme. [See the discussion on this website of Quintiles and Quality.]
By the "truth standard", hs-CRP provides a test that is truly related to the risk of future cardiovascular events, the new high sensitivity measurement systems make it possible to measure it correctly, but the criterion for "nothing but the truth" is not satisfied. The biologic variability of the individual patient can potentially confound the use and interpretation of the test, as well as the analytical variability and the difficulty of quality controlling the test.
Here's a chance to watch the truth unfold and to see if science and scientists are truly objective. Over the course of the next few years, we will learn the truth about the clinical usefulness of hs-CRP measurements on the patient population at large.