July 2009 Archives

An article published by the Cleveland Clinic's Dr. Mary Bronner, outlines the steps involved in a biopsy procedure in great detail.  It turns out there are 18 different steps involved, and the number of times a particular tissue sample changes hands is significant.  The steps to this extremely complex process are explained below (note: numbers have been added by the author):

"Considering the numerous medical professionals involved in processing a tissue sample from the patient to the pathologist reviewing it microscopically, it is truly a marvel that so few errors occur. Consider that from the patient, a biopsy sample or surgical resection specimen is initially (1) handled by the treating physician using carefully cleaned biopsy and surgical tools that have been used previously to obtain many other patients' samples. One or more nurses or other assistants assist the physician in (2) getting the tissue sample into a properly labeled specimen container. The specimen container is (3) batched with many other containers and (4) transported to the pathology laboratory. There, the specimen is (5) accessioned into the pathology computer system and is (6) assigned a unique surgical pathology identifier. Next, the paperwork and specimen container are (7) processed by a pathology assistant, resident, or pathologist who removes the specimen from the labeled container and examines and describes the tissue grossly. The tissue is (8) dissected by carefully cleaned instruments that also are used to dissect many other patients' samples. The specimen is (9) divided among a number of tissue cassettes, small plastic containers, which are (10) labeled individually with the surgical pathology number and a unique block number. The tissue cassettes have holes in them to permit flow of the various processing fluids required to process the tissue chemically into a final wax tissue block. Many hundreds of different patients' cassettes are (11) placed into a common chemical bath for this processing stage. Rarely, a tissue fragment from one patient can exit its cassette and enter through the cassette holes of another patient's block to become part of this second patient's block. A histotechnologist uses clean forceps, which are cleaned and used subsequently on many other patients' specimens, to (12) pick up the wax-infused tissue fragments from the processing cassettes and place them into the final wax tissue block that will be used to section the actual histologic slides. Another histotechnologist (13) sections 5 μm slices on a razor blade affixed to a microtome. These thin wax slices are (14) floated onto a carefully cleaned water bath, which has had many other patients' wax slices previously floating in it. Floating allows slices to flatten and be (15) transferred onto a glass slide, which has been hand-labeled by the histotechnologist. The slide later receives a permanent computer-generated slide label that is (16) affixed to the slide by another technician. Finally, all of the slides on any given patient's procedure are (17) assembled with the accompanying paperwork and (18) delivered to the pathologist for diagnostic interpretation. A mistake leading to inadvertent tissue contamination can occur at any one of the above logistically complex processes.[1]"

 
In learning more about this process, it is impossible not to see just how many opportunities there are for error.  Even with quality assurance checkpoints in place, the misidentification or switching of biopsies from time to time is inevitable.  With the introduction of the know error® specimen security system with unique patient code and DNA identity confirmation, we are able to catch switching errors that would be otherwise undetected by existing quality assurance systems.  The know error® system identifies biopsy identity switches before a patient suffers an adverse outcome (i.e., under treatment/overtreatment).

To learn more about the know error® specimen security system, visit www.knowerror.com.

[1] DNA Fingerprinting Analysis for Specimen Identification  http://referencelab.clevelandclinic.org/DBSearch/TestDetail.asp?ID=2676

Numerous studies, including one published by the College of American Pathologists in 2006, have revealed that "misidentification errors are common in laboratory medicine"[1].  While most medical mix-ups are caught by quality assurance processes already in place, those that are not can have devastating consequences.  "Everyone makes mistakes" is something often heard in everyday conversation, but when it comes to an error as significant as the switching of a biopsy result, a simple mistake can lead to adverse patient outcomes.  These adverse medical outcomes have both medical and legal consequences for every person and / or entity involved in the biopsy process.

The know error® specimen security system virtually eliminates the possibility that an identification switching error will result in an adverse patient outcome.  Utilizing existing forensic DNA science, it was designed to increase patient safety and the quality of patient care. It represents an important innovation in the process of evaluating biopsies.  There are 3 basic steps to the know error® system - 1) Swab, 2) Sample and 3) DNA Match.  These steps are outlined below in greater detail. 

To make the process more relatable, we'll be using a hypothetical patient - let's say "Mr. Smith"--  who will be going in for a prostate biopsy.

First, it should be explained that Mr. Smith's doctor incorporates the know error® system -- a comprehensive biopsy kit that includes all of the necessary materials to be used in obtaining a sample of Mr. Smith's DNA as well as all of the materials that will be used by the doctor performing the biopsy to collect Mr. Smith's tissue samples.

Now let's take a look at the know error® system in action:

1) Swab:  Before Mr. Smith goes in for his biopsy, a DNA sample is taken by swabbing the inside of his cheek.  Mr. Smith will sign the envelope containing his DNA sample and a uniquely bar-coded patient ID label.  The swab is then sent to an independent forensics lab along with Mr. Smith's unique bar-coded patient ID.

2) Sample: Mr. Smith's same unique patient ID is attached to his file along with all of the other materials in the biopsy kit that will be used by the physician collecting his prostate tissue samples.  Once Mr. Smith's biopsy has taken place, the tissue samples collected will be placed in containers with his bar-coded patient ID and sent to the pathology lab.  Once Mr. Smith's samples arrive at the lab, the bar-coded label will be checked before any testing begins.

3) DNA Match:  If Mr. Smith's biopsy results reveal that he does have cancer, this will trigger the third step of the know error® system process, and small "scrolls" of his tissue samples will be sent to the same forensics lab where his reference DNA sample (the swab) was already sent.  The lab will analyze the biopsy tissue and compare it to Mr. Smith's DNA sample confirming a DNA match.  The DNA match of Mr. Smith's cheek swab and his biopsy tissue samples will give him complete confidence in knowing that he does have cancer and that his doctor's treatment recommendation is based on his biopsy results. 

In cases where a DNA match is not confirmed, the forensics lab will know the biopsy tissue samples have been switched with those of another patient. At that point, the lab will notify the appropriate parties to rectify the situation. 

Only by implementing an innovative specimen security system such as the know error® system can the medical community be assured that specimen misidentifications are detected before a patient suffers an adverse outcome. For each switch identified by the know error® system, all parties involved -- patients, physicians, and pathology labs -- are protected from potentially devastating consequences.   

To learn more about the know error® specimen security system, visit www.knowerror.com

[1] Valenstein PN, Raab SS, Walsh MK. Identification errors involving clinical laboratories: a College of American Pathologists Q-Probes study of patient and specimen identification errors at 120 institutions. Arch Pathol Lab Med. 2006