Going in the wrong direction

September 21, 2009


Here are some comments (some paraphrased) and suggestions made on a blog about adapting the Aviation Safety Reporting System to reduce the rate of medical errors.

Incident reporting provides “no useful information about the true frequency of errors in an institution.” It’s too expensive, it takes too much time. There’s too much data. We should only report errors that cause temporary or serious harm.

These comments were made by Robert M. Wachter, MD. From his blog’s bio …

 “He has published 200 articles and 6 books in the fields of quality, safety, and health policy. He is also a national leader in the fields of patient safety and healthcare quality. He is editor of AHRQ WebM&M, a case-based patient safety journal on the Web, and AHRQ Patient Safety Network, the leading federal patient safety portal.”

There are two ways to reduce the rate of medical errors.

  1. Lower the probability of errors that have not yet occurred
  2. Lower the rate of errors that have occurred.

The Aviation Safety Reporting System is an example of tackling #2.

Many (most) errors do not directly cause harm – they have the potential to cause harm. This can be understood be mapping out each medical procedure. To suggest to not report all errors will shortchange the system.

The most important errors receive focus by using a Pareto chart or table. The fastest way to reduce error rates relies on a suitable ranking system.

All of this takes time, training, and commitment.

Some successful medical examples: anesthesiology improvements in the 70s 80s (1). The recent reduction of infections in placing central lines (2).

Dr. Wachter is going in the wrong direction.


  1. Cooper JB, Newbower RS, Long CD, McPeek B: Preventable anesthesia mishaps: A study of human factors. ANESTHESIOLOGY 1978; 49:399-406. An online version of Paper 5 can be found at http://qshc.bmj.com/content/vol11/issue3/#CLASSIC_PAPERS
  2. Pronovost P. et al. An Intervention to Decrease Catheter-Related Bloodstream Infections in the ICU. N Engl J Med 2006;355:2725-32

PS – A commentator who agrees with Dr. Wachter offers a standard bit of resistance to using the Aviation Safety Reporting System in medicine – We’re different – medicine is more complicated.

Bernie Madoff of Clinical Chemistry?

September 11, 2009


There is/was? a promising marker for prostate cancer called EPCA-2 (1). The person who discovered the test is now being sued by the company that licensed the marker (2). According to the lawsuit:

“Notwithstanding the spectacular (and false) results proclaimed by defendants, the Getzenberg assay was no more accurate in distinguishing cancerous tissue from normal tissue than flipping a coin,”

Among the coauthors in reference 1 are well known clinical chemists. They may have a lot of explaining to do.

Another well known clinical chemist questioned the validity of the results (3). He may be looking pretty good when all of this gets straightened out.

We shall see.


  1. Leman ES, Cannon GW, Trock BJ, Sokoll LJ, Chan DW, Mangold Ln Partin AW, Getzenberg RH. EPCA-2: a highly specific serum marker for prostate cancer. Urology. 2007;69:714-20.
  2. http://www.pittsburghlive.com/x/pittsburghtrib/news/pittsburgh/s_641304.html
  3. Point:EPCA-2: A promising new serum biomarker for prostatic carcinoma? Diamandis EP. Clinical Biochemistry 2007;40:1437-1439.

Wrong thinking about glucose standards

September 2, 2009


Glucose has been in the news lately both in the New York Times and the medical literature.

A standard favoring tight glycemic control was dropped, possibly because the glucose meters used were inaccurate (1-3.)

Glucose meters that use glucose dehydrogenase can give very wrong answers in dialysis patients (4).

And finally, the FDA is considering revising glucose standards (5). This blog entry is about glucose standards revision. The article mentions that FDA is considering revising the performance standards in ISO 15197 which are: 95% of values must be with 20% of reference at 75 mg/dL or above and within 15 mg/dL below 75 mg/dL. The Boyd and Bruns modeling paper is referenced and Bruns is quoted in the article. I have previously critiqued the Boyd and Bruns paper (6).

Here is the main point which is not covered in the article. The main problem with the ISO standard is that it specifies performance for only 95% of the data. This of course leaves up to 5% of the data as unspecified and means that if up to 5% of glucose results had large enough error so that hyperglycemic patients were classified as hypoglycemic and vice versa, that assay would be acceptable according to ISO. This is equivalent to saying that up to a 5% wrong site surgery rate is acceptable! 100% of the data must be specified as is the case with glucose error grids, which predated the ISO guideline.

A second problem with the ISO guideline is that the performance limits ignore user error. But user error contributes to the final result and must be part of the performance specification.

The protocol must also be part of the guideline. In a short method comparison, it is possible to observe no large errors. To supplement this, specific analytical properties of the assay must be specified as well as risk management criteria. There are recent glucose recalls where software was faulty and allowed units to be changed from mg/dL to mmol/L or vice versa without customer knowledge.

I mention in passing that the Boyd and Bruns article referred to the article underestimate total user due to an inadequate model which fails to account for interferences. Reference 4 is an example of interferences and responsible for at least 13 deaths.


  1. See: http://www.nytimes.com/2009/08/18/health/policy/18diabetes.html?_r=1&scp=1&sq=glucose&st=cse
  2. Intensive versus Conventional Glucose Control in Critically Ill Patients. NEJM 2009;360:1283-1297
  3. Scott MG, Bruns DE, Boyd JC, and Sacks DB. Tight glucose control in the intensive care unit: Are glucose meters up to the task? Clin Chem 2009;55:18-20.
  4. See: http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/PatientAlerts/ucm177189.htm
  5. See: http://www.aacc.org/publications/cln/2009/september/Pages/inside0909.aspx
  6. Krouwer, JS. How to Improve Total Error Modeling by Accounting for Error Sources Beyond Imprecision and Bias, Clin Chem 2001;47:1329-30.