Abstract
The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, see http://journals.sagepub.com/doi/10.1177/2374289517715040.
Keywords
Primary Objective
Objective GP1.1: Pre- and Postanalytical Errors
Give examples of common sources of preanalytical and postanalytical errors and categorize errors when the following procedures are not properly followed: pairing patient/specimen identification with the requisition forms, using correct specimen containers/tubes for specific tests, and timing of collection, transport, and storage.
Competency 3: Diagnostic Medicine and Therapeutic Pathology; Topic GP: General Principles; Learning Goal 1: Laboratory Tests.
Patient Presentation
A 35-year-old woman is scheduled for a tubal ligation, and a preoperative type and screen is sent. She had never been transfused at this facility. A type and screen was drawn 6 months ago and showed that she was A positive with a negative antibody screen.
Diagnostic Findings, Part 1
Results from the current type and screen revealed the sample was O positive with a negative antibody screen.
Questions/Discussion Points, Part 1
What Are the First Steps Taken Upon Sample Receipt?
Check that the sample is labeled with 2 identifiers. AABB publishes standards that are required to ensure the safety of blood products in all steps from donation of blood to testing of blood products to transfusion of blood products. Standards specifically indicate that “identifying information for the patient and the sample shall correspond and be confirmed at the time of collection using two independent identifiers.” 1,2 Another standard says that “the transfusion service shall confirm that all identifying information on the request is in agreement with that on the sample.” 1,2 The purpose of using 2 identifiers is to ensure that the blood sample is from the correct patient, and should that patient need blood products, the correct blood products can then be issued.
Review the patient history
The history review is a required step in sample processing. The standards indicate that “there shall be a process to ensure that the historic records for the following have been reviewed…ABO group and Rh type.…These records shall be compared to current results, and any discrepancies shall be investigated and appropriate action taken….” 2,3 The purpose of reviewing the historic records is to help ensure that if there is an accidental mislabeling of a patient sample, it will be identified before any blood products are administered to the patient.
What Possible Explanations Should Be Considered?
Except in 1 particular circumstance, the blood type of a patient should not change. There are a limited number of possible explanations for the current findings. The current sample could be from the wrong patient. The sample taken 6 months ago could have been from the wrong patient. Or, if the patient had a stem cell transplant in the interval from a type O allogeneic donor, her blood type could have changed.
What Should the First Steps Be to Determine the Etiology of the Problem?
There are 2 very important steps that need to be completed to investigate a possible mislabeling of a blood sample. The first is to get the history to be sure the patient did not have a transplant, and in addition to ask for another sample to be drawn from the patient to see whether it matches the historical data or the data from the current blood sample.
Diagnostic Findings, Part 2
Evaluation reveals that the patient has not had a stem cell transplant. A second sample is sent for evaluation which is determined to be A positive, negative antibody screen.
Questions/Discussion Points, Part 2
What Are Your Conclusions?
The sample drawn earlier that day was from the wrong patient. The phlebotomy area should be alerted as there may be another incorrect sample if this was a single direct switch of identifiers on the tube (another patient who is really an O may have been typed as an A). For patients that are hospitalized, it is just as important to evaluate where the blood sample came from and investigate if there could be an accidental mislabeling of samples.
Diagnostic Findings, Part 3
A second patient was not found.
Questions/Discussion Points, Part 3
What should be done in follow-up of this event?
Follow-up regarding process control, patient identification, and labeling should be done. This should include a review of the training and competency of any involved health-care professionals, which may reveal the need for additional training.
Teaching Points
Patient identification is critical to patient safety and diagnostic accuracy.
Possible patient identification errors must be investigated fully and promptly, as more than 1 patient may be involved.
Reducing errors requires strict adherence to clinical procedures. In this example, samples must be labeled with 2 identifiers in the presence of the patient. All identifying information on the request must be in agreement with the sample label. The history review is a required step in specimen processing.