Error Reduction in the Preanalytical Process

© Springer Science+Business Media New York 2015
Raouf E. Nakhleh (ed.)Error Reduction and Prevention in Surgical Pathology10.1007/978-1-4939-2339-7_4

4. Error Reduction in the Preanalytical Process

Richard W. Brown 

System Laboratory Services, Memorial Hermann Healthcare System, 7600 Beechnut, Pathology, 2nd Floor, Houston, TX 77074, USA



Richard W. Brown

ErrorHistologyMislabelExtraneous tissueParaffin blockSlidesEmbeddingGrossingAccessioningSpecimen


Historically, the histology laboratory has not been regarded as a significant source of error in anatomic pathology; the focus has been primarily on errors in diagnosis. However, the production of a microscopic section for pathologist review and diagnosis is a complex, error-prone process with many handoffs and manual processes, including specimen accessioning and grossing , tissue processing and embedding , the cutting and flotation of tissue sections onto microscopic slides , and the process of slide “sign-out,” in which the microscopic slides are reviewed for quality, matched with typed gross descriptions, and distributed to the pathologist. As these processes occur before the pathologist reviews the case microscopically and determines a diagnosis, they have been collectively termed the “preanalytical” phase [1].

Troxel was among the first to call attention to preanalytical processes as a source of error. In a review of pathology malpractice claims from 1998 to 2003, he documented a significant increase in what he termed “operational errors” as the cause of the claim, 8  versus 1.2 % in a prior study of claims from 1995 to 1997 [2, 3]. Among these, the most common error leading to misdiagnoses was a specimen mix-up between two patients followed by the presence of extraneous malignant tissue from another case, lost tissue, and mislabeled slides; others have affirmed these categories of error as of greatest clinical importance [4, 5]. In contrast to earlier studies that focused on the analytical phase (i.e., diagnostic errors) , in a survey of 34-member laboratory directors from the Association of Directors of Anatomic and Surgical Pathology, published in 2006, 53 % of the respondents indicated that most of the errors in anatomic pathology occur in the preanalytical phase [6].

The most comprehensive data regarding preanalytical errors has been gathered through the Q-Probes studies of the College of American Pathologists. In a study of 1,004,115 cases from 417 institutions, 6 % of the cases were reported to have defects in specimen identification and accessioning [7]. A subsequent study of 427,255 cases from 136 institutions documented a rate for misidentification and/or mislabeling of 0.11 %, with a rate of 0.1 % for specimens, 0.17 % for tissue blocks, and 0.11 % for slides [8]. This study noted that errors occurred most frequently at the time of accessioning, when transferring tissue into blocks and when sections were cut and transferred onto glass slides , and also documented that laboratories in which specimens were handled one at a time had a lower frequency of mislabeling errors. Finally, a study of 321,577 retrospectively reviewed and 57,083 prospectively reviewed slides from 275 laboratories documented extraneous tissue in 0.6 and 2.9 % of slides examined, respectively [9].

Meier et al. in a review of amended reports developed a “taxonomy” of defects that included: (1) misidentification (patient, tissue, laterality, or anatomic localization); (2) specimen defects (lost, inadequate size/volume, absent or discrepant measurements, inadequate representation); (3) misinterpretation; and (4) report defects. In that study that documented an amended report rate of 4.8/1000, misidentification and specimen defects, the preanalytical variables, accounted for 19 and 9 %, respectively, of the amendments; in a later multi-institutional validation study, these defects caused 20–38 % and 4–10 % of the amendments [1012]. In an 18-month study encompassing 29,479 cases, Layfield demonstrated a 0.25 % rate of mislabeled cases, 0.068 % mislabeled blocks, and 0.030 % mislabeled slides [13]. The majority of the errors were made in the grossing room by a grossing assistant. Of the 75 labeling errors, 13 (17 %) could have substantially harmed the patient, if not identified. Changes in pathology practice, such as the advent of laboratories processing only one specimen type (e.g., gastrointestinal or prostate biopsies) have introduced a greater potential for misdiagnosis of malignancy because the opportunity to identify an error based on mismatched tissue types is eliminated. Indeed, a recent study by Pfeifer et al. of 13,000 prostate needle biopsies from 54 laboratories, studied prospectively with a molecular assay to confirm patient identity, identified a rate of transposition between two patients of 0.26 % (0.06–0.37%), and a rate of tissue contaminant from another patient of 0.67 % (0.27–0.93 %) [14].

In general, the first step in error reduction is in the identification of process issues and their prevalence. Individual occurrences can be mapped effectively through the use of root cause analysis or failure modes and effect analysis [1, 1517]. Direct observation can also identify key defects; one observational study of specimen accessioning and grossing documented a remarkable 5.5 near-miss events (errors identified during the process) per specimen [18]. Zarbo and colleagues at The Henry Ford Hospital have emphasized the utility of blameless error self-reporting and implementation of the Henry Ford production system, with short-term focused review of practices, as a method for identifying process defects [19, 20]. In their initial study, 27.9 % of surgical pathology cases contained defects, leading to an amended report rate of 2.4 %; these defects included issues with specimen receipt (8.3 %) but much more commonly in accessioning (24.9 %), gross examination (20.0 %), and production of histologic slides (30.8 %) and recuts (13.4 %). This study also documented identification defects in 1.67 % of cases with mislabeling of slides and blocks accounting for 78 % of these defects.

Nakhleh has focused attention on process issues leading to laboratory error and those issues particularly applicable to histology laboratories, including: (1) variable input, (2) complexity, (3) inconsistency in training and procedures, (4) the need for human intervention, (5) time constraints, (6) frequent handoffs, and (7) an inflexible hierarchical culture that is unable to adapt and change or to acknowledge the source of errors [21, 22]. He proposed a number of global error reduction strategies, including:

  • Built-in QC processes that decrease reliance on vigilance

  • Use of standardized operating procedures

  • Simplification of processes, with a specific effort to reduce the number of handoffs

  • Implementation of processes to detect errors

  • Attention to human resource issues, including adjustments in work schedules, in order to minimize time constraints, adjustments to the workplace, in order to minimize distractions, adequate training, and assuring that staff with the proper skill set are assigned to each position

Raab and colleagues have demonstrated the efficacy of a lean-based quality improvement program, which allowed that group to decrease near-miss events in the preanalytical workflow from 5.5 per specimen to 1.8 [23]. More recently, there has been significant focus on the use of barcodes , assigned at the time of accessioning that can be applied to, and read from, all tissue cassettes, paraffin blocks , and microscopic slides that are derived from a specimen, providing unambiguous identification throughout the entire histology process [24, 25]. Zarbo and colleagues decreased their misidentification rate from 1.67 to 0.63 %, including a 95 % reduction in glass slide misidentification, through the use of a bar-coded system accompanied by process redesign [24]. Radiofrequency devices have received similar attention for specimen tracking [26]. While these innovations can significantly reduce the preanalytical error rate, they are in place at a relatively small number of laboratories; therefore, the discussion that follows focuses on manual processes, considering each of the steps in the preanalytical process, the potential sources of error and error reduction strategies.

Accessioning and Grossing

Potential Sources of Error

The preanalytical process in surgical pathology begins when the specimen is received in the frozen section or histology laboratory , and is accessioned into the laboratory information system. The first opportunity for specimen mishandling, and therefore the error, is in the operating room, physician office, interventional radiology or endoscopy suite from which the specimen arises. The practice of preparing specimen containers and labels prior to a procedure is common, and therefore, there is significant opportunity to pair a specimen from patient B with the labels from patient A who was previously in that room. One study from a large surgical service documented an error rate of 4.3/1000 specimens with unlabeled specimens, empty containers, incorrect laterality or tissue site, incorrect patient, no patient name, and no tissue site identified representing the most common errors [27]. While it is possible to effect error reduction through strict adherence to a policy that requires a matching of two patient identifiers at every step of the process and accountability in the form of requirements for provider initials on the specimen container to verify proper identification and the presence of tissue in the container, in reality these processes are beyond the control of the laboratory [28]. Therefore, the true opportunity for error reduction begins at the time of accessioning .

When specimens are received in the laboratory, the specimen identification on each container should be rigorously matched with the specimen requisition , with confirmation that there is a match in the patient using two patient identifiers and an exact match in the specimen source. Failure to do so introduces an opportunity to assign one or more specimens to the wrong patient, a serious error if a malignant diagnosis is involved. Similarly, if the accessioning personnel do not carefully match the patient name and a second identifier, typically date of birth or medical record number, it is possible to erroneously accession the case to the wrong patient, one who shares a name with the index patient. When the accessioning is complete, there should be a unique case number associated with specimens from one patient as well as a unique alphanumeric designation for each part of that accession. For example, a uterus with separately submitted adnexa might be accessioned as S-year-unique number (e.g., S-13-4506) with parts A (uterus), B (right fallopian tube and ovary), and C (left fallopian tube and ovary). Another opportunity for error exists when the specimens are not correctly matched with the alphanumeric designation.

The next step in the process of accessioning is the labeling of tissue cassettes. There are three essential elements to a cassette label: the case number, the alphanumeric designation of the specimen, and a sequential label for each cassette within that specimen. The latter should then be specifically identified in a gross description. For example, a cassette labeled S-13-4506 A1 in the example above might contain sections of uterine cervix while S-13-4506 A2 might contain a section of uterine serosa, and S-13-4506 B2 a section of fallopian tube. Incorrect cassette labeling, with a failure to detect the error at the time of tissue submission, can result in an incorrect diagnosis, when, for example, cassette A1 in a cancer resection contains a surgical margin and cassette A11 does not.

Perhaps, the greatest opportunity for error is in the process of submitting tissue for microscopic examination (“grossing”) . The prosector could potentially: (1) erroneously submit tissue in a cassette belonging to a different patient (tissue from case 4506 submitted in a cassette labeled 4507), (2)submit tissue in the wrong cassette within a case (in the example above, the margin is submitted in A11 instead of A1), or (3) inadvertently submit extraneous tissue . The latter typically occurs when the prosector is submitting tissue from more than one case at a time, or when the workspace and instruments have not been adequately cleaned after each accession, providing an opportunity for inadvertent tissue carryover from case to case. Finally, error can occur as the result of inadequate dictation of the macroscopic findings as they relate to the tissue cassettes submitted. Common errors in this category are failure to unambiguously identify each of the surgical margins with ink of a designated color in cancer resection cases, and failure to provide a “section code” that links each tissue cassette submitted to a particular tissue site or lesion.

Strategies for Error Reduction

  • At the time of accessioning, each specimen container should be matched to the requisition. Both the tissue source and the patient name and second identifier (medical record number, date of birth) must match exactly. If they do not or if a specimen container is received unlabelled, the submitting nurse or physician should be notified immediately and the inconsistency resolved; any delay in this notification will likely result in the inability to adequately resolve the discrepancy, as the labeling staff may no longer be on duty. Cases with incorrect data should never be accessioned until the inconsistency has been addressed, either by a correction or by a discussion with the submitting physician. This resolution should be documented in an error log maintained either in written form at the bench or in the laboratory information system (LIS). In addition, all specimen containers should be visually inspected for the presence of tissue and, if tissue is not present, a similar approach to remediation and documentation should be applied.

  • Accessioning personnel must be trained to check each patient’s full name, as it appears in the LIS, and a second unique identifier against the requisition and specimen container as the case is entered to ensure that the case has been accessioned to the correct patient .

  • Tissues of the same type (e.g., prostate or breast needle biopsies) should not be accessioned sequentially. This significantly decreases the likelihood for diagnostic error , in that, if there is an error in submitting the tissue between two cases, the different tissue type involved should be readily apparent. It is recognized that there will always be cases in which this is not possible (e.g., GI, skin, or prostate biopsy only laboratories). In these instances, use of colored inks or alternating color cassettes may be of similar utility.

  • Best practices in cassette labeling include: (1) using an automated cassette printer linked to, and driven by, the LIS; (2) labeling each case as it is grossed, rather than labeling multiple cases and lining them up with the containers in advance; and (3) including a full or partial patient name on each cassette. It is recognized that these may not be achievable goals in every laboratory.

  • Tissue cassettes that have been prelabeled should be checked for accuracy by both the grossing assistant, if applicable, and by the prosector, matching both the accession number and the alphanumeric designation before the tissue is placed into the cassette.

  • Only one case should be grossed at a time. At the conclusion of the case, all paper towels or pads on which the tissue was grossed should be discarded, and all instruments carefully cleaned and wiped dry to avoid contaminants. All unused tissue cassettes from that case should be discarded.

  • Small biopsies should not be transferred to the cassette using forceps. A lens paper or mesh bag should be inserted inside a funnel and the specimen contents should be poured directly into the paper or bag; this practice essentially eliminates the possibility of introducing contaminant tissue.

  • For cases with multiple cassettes containing different tissue types or sites, the gross description should include a section code designating the origin of the tissue in each cassette. For complex cases, it is prudent to write the section code as sections are submitted and dictate the code at the conclusion of the case. For tumor cases with margins, an ink code should also be included that matches the ink colors with the margin they are meant to designate.

  • The laboratory should maintain a written log that specifies the number of blocks taken from each specimen, the type of tissue they contain; and, if these logs are available to embedding and sign-out personnel , the number of tissue pieces submitted. Any special instructions (e.g., decalcification) should be included as well.

Tissue Processing and Embedding

Potential sources of Error

After the process of specimen grossing and tissue submission, tissue cassettes are processed through dehydrating solutions and paraffin. In most laboratories, this is accomplished by automated tissue processers that are driven by a user-defined processing schedule. The paraffin-impregnated tissues are then re-embedded into the same tissue cassettes in which they were submitted, with additional paraffin as needed, in order to provide a tissue surface that can be subsequently trimmed and sectioned by the histotechnician performing microtomy. With the increasing number of multi-site laboratories, it is increasingly common for tissue cassettes to be transported to a core laboratory for processing. There are three major opportunities for error in these processes: (1) tissue is lost, either a portion of tissue within a single cassette or one or more tissue cassettes in their entirety, (2) tissue cannot be adequately examined microscopically due to inappropriate tissue processing, and (3) extraneous tissue (i.e., tissue from another patient) is introduced inadvertently. In general, tissue cassettes are fenestrated, with parallel slits or small, round holes that allow processing fluids to flow freely through the cassette. Although these fenestrations are of small diameter, it is theoretically possible for minute tissue fragments to flow into or out of a cassette during processing, leading to a loss of tissue or gain of extraneous tissue fragments. Much more commonly, however, these misadventures occur at the time of embedding , when the embedding personnel do not carefully observe the number of tissue fragments to be embedded, work on more than one case at a time, and/or do not rigorously clean the embedding forceps between cases. Tissue processing is beyond the scope of this discussion; however, for purposes of error reduction the avoidable sources of error leading to loss of tissue integrity, and therefore, the potential for an erroneous interpretation due to poor visualization of microanatomy, include: (1) submission of tissue of inappropriate size, (2) inadequate time in formalin fixative prior to processing, and (3) failure of personnel loading the tissue processers to recognize that a tissue is of inappropriate type for the processer onto which it is loaded (e.g., a small biopsy processed using a schedule intended exclusively for large tissues).

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Oct 29, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Error Reduction in the Preanalytical Process

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