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As many as 3.5% of prostate biopsy specimens were contaminated or inadvertently switched with that of another patient, according to a review of 13,000 samples from 54 laboratories.
The overall error rate was less than 1%, but rates among different types of labs ranged as high as 3.51%. No laboratory included in the study had an error-free performance record.
Institutional approval for the study required investigators to remove all identifying information from the specimens. Consequently, the impact of the laboratory errors could not be assessed, as reported online in the American Journal of Clinical Pathology.
"It is possible that in a subset of cases, the adenocarcinoma from the foreign patient that was the source of the extraneous tissue exhibited sufficiently similar characteristics of the target patient such that either patient's diagnosis would have resulted in the same course of therapy," John D. Pfeifer, MD, PhD, and Jingxia Liu, PhD, of Washington University in St. Louis, wrote of their findings.
"Regardless of the portion of cases in which patients may have, by chance, received the correct treatment despite the specimen identity error, the fact remains that ... a diagnosis was assigned to the wrong patient with no knowledge or even suspicion of the error that had occurred."
The study examined the frequency of occult "specimen provenance complications" (SPCs), errors that occur without any indication of a problem. SPCs arise when specimens are matched to the wrong patients (type 1 error) or when one patient's specimen is contaminated by tissue from one or more other patients (type 2 error).
SPCs have obvious implications for patient safety and medicolegal actions, the authors noted in their introduction. However, the frequency with which these errors occur has remained unclear.
To describe the rates of both types of SPCs, Pfeifer and Liu analyzed data for 13,000 prostate biopsy specimens obtained in routine clinical practice. The specimens were processed by a variety of surgical pathology and urology group practice laboratories.
Data for the study came from Strand Analytical Laboratories, an Indianapolis company that has developed a DNA-based test for occult SPCs. The test employs short tandem repeat (STR) analysis, originally developed by the FBI.
"STR analysis has been shown to be particularly useful in identifying occult specimen identity errors," the authors noted in their introduction.
The investigators grouped the 54 laboratories into five categories based on work flow, location, and management structure: physician-owned labs within a group-practice setting, independent reference labs, hospital labs, nonphysician owned labs located in facilities shared with group practices, and labs that have the technical histopathology and professional pathology in separate facilities, necessitating transport of specimen slides.
The error rate for all labs combined was low: 0.26% for type 1 errors and 0.67% for type 2 errors. However, the authors pointed out, each SPC involved at least two patients, "the target patient and the foreign patient (or patients) whose tissue was misidentified as originating from the target patient."
Reference laboratories had the highest rate of SPCs: 0.37% for type 1 and 3.14% for type 2, resulting in an overall error rate of 3.51%.
Only one clinical trial has attempted to document SPCs, according to the authors. The Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial took steps to measure the rate of SPCs after three cases of occult biopsy specimen misidentification occurred during the first 2 years.
The rate of type 1 errors was 0.4% during the first 2 years of the REDUCE trial and declined to 0.02% in the final 2 years, after investigators implemented changes in specimen-handling procedures. A type 1 error rate of 0.5% persisted throughout the trial for blood samples that served as reference specimens.
Based on their study, the authors suggested that prospective DNA testing to confirm the identity of prostate biopsies that show adenocarcinoma may be useful for preventing treatment errors stemming from misidentification.
Strand Analytical Laboratories, which developed a test for STR analysis, provided the data for the study.
The authors had no relevant disclosures.
Charles Bankhead
Staff Writer
Working from Houston, home to one of the world's largest medical complexes, Charles Bankhead has more than 20 years of experience as a medical writer and editor. His career began as a science and medical writer at an academic medical center. He later spent almost a decade as a writer and editor for Medical World News, one of the leading medical trade magazines of its era. His byline has appeared in medical publications that have included Cardio, Cosmetic Surgery Times, Dermatology Times, Diagnostic Imaging, Family Practice, Journal of the National Cancer Institute, Medscape, Oncology News International, Oncology Times, Ophthalmology Times, Patient Care, Renal and Urology News, The Medical Post, Urology Times, and the International Medical News Group newspapers. He has a BA in journalism and MA in mass communications, both from Texas Tech University.
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