The Case

A 22-year-old unmarried woman came to her doctor’s office worried that she might be pregnant. Although she did not want to have a baby at that time, she stated that she would carry the pregnancy to term if she were pregnant.

The patient collected her own urine sample and placed it in the specimen cabinet, which opens into the laboratory. A urine specimen already placed in the cabinet by a different patient had not yet been labeled and processed by the lab technician. Five minutes later, the physician was informed that the pregnancy test was negative. The physician conveyed this result to the patient, much to her great relief.

After the physician left the room, he was informed that the two specimens had likely been switched. The other urine sample belonged to a diabetic patient; the technologist suspected a mix-up after a urine dipstick on that sample indicated elevated glucose. Both patients were asked to resubmit urine samples; in fact, the patient was pregnant.

The physician was placed in the awkward position of informing the patient that the samples had been switched, and appropriate sympathetic counseling was made more difficult.

The Commentary

Some might argue that this case is a near miss as the technologist caught the mistake relatively quickly—before the patient even left the office. However, this case does represent an error and preventable adverse event, because the patient experienced some emotional harm. Certainly, the outcome of this error could have been far worse. It was fortuitous that the laboratory technician realized that the samples had been swapped due to the presence of glucose. One could imagine this error remaining undiscovered until the patient presented months later with clinical signs of pregnancy. In the interim, the patient might have acted in ways potentially harmful to the pregnancy.

Little is known about errors and adverse events in the outpatient setting. Approximately 8%-9% of adverse events occur in physicians’ offices.(1) Recent studies have examined adverse drug events in ambulatory settings (2,3) and adverse events related to the inpatient–outpatient interface.(4,5) Hundreds of millions of laboratory tests are ordered annually in primary care practices, yet little is known about how often laboratory errors occur in primary care.

Laboratory testing can be broken down into three phases: pre-analytic (test ordering, specimen collection, and handling), analytic (test performance), and post-analytic (result handling and communication). Because of improvements in and automation of laboratory procedures, most laboratory errors occur during the pre-analytic and post-analytic phases of the testing process. A literature review found that laboratory errors in the pre-analytic phase ranged from 32%-75% of all errors.(6) In another study, 39% of lab errors involved misidentification of the requested tests, the requesting doctor, and/or the patient.(7) In another article describing the epidemiology of lab errors prompting incident reports, pre-analytic errors occurred in 71%, with specimen transportation being the most common.(8)

There are few published studies of laboratory error rates in the outpatient setting. An outpatient study published in 1996 (9) assessed 124 primary care clinicians in 49 practices in the United States and Canada. Clinicians were asked to report any irregularities in the laboratory testing process during a 6-month period. A total of 180 laboratory problems were detected, for a crude frequency of 1.1 laboratory problems per 1000 patient visits. Of 180 reported problems, 49 impacted patient care (27%). Of these, 10 (6% of total) had a significant effect on patient care. Problems detected in the pre-analytic phase were most common (55.6%) and specimen handling and collection problems were the most common overall (33.9%), similar to the urine mishandling case presented here. Given the known low yield of self-reporting (10), this study’s results probably represent only the "tip of the iceberg."

Unlike in the inpatient setting, where caregivers typically procure and transport laboratory specimens, in the outpatient setting patients are often responsible for collecting and transporting their own samples. This is a potential set-up for patient identification errors or specimen mishandling errors. In this case, the patient placed the urine specimen in the cabinet adjacent to the lab. Often, patients deliver throat swabs, lab requisitions, x-rays, and other clinical items to various sites of outpatient care. Therefore, verification of patient identification and proper labeling of specimens, requisitions, and clinical information in general is crucial. However, this process often breaks down. Sample labels are often handwritten with minimal information (eg, "Smith" when there could be multiple Smiths in the clinic that day). In addition, samples may not be labeled at all, or may be labeled only after the patient has left.

Primary care practices and testing facilities should take a proactive process redesign approach to the issue of laboratory errors, particularly those associated with pre-analytic or specimen handling errors. Techniques such as failure modes effects analysis (FMEA) (11) can help to map out the laboratory specimen process and all the potential ways in which failures (or errors) can occur. Then, clinical staff can collaborate to design fail-safe mechanisms for ensuring proper specimen identification and handling during the pre-analytic phase of testing. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has mandated that two forms of patient identification should be used for blood samples (12), and this should apply to any kind of lab specimen. This patient verification should occur at the time a specimen is labeled, and the label should include at least two identifiers (ie, full name and birthdate). In addition, specimen collection bottles should be labeled before the patient provides the sample. Labels should be legible and should never be left in a window or deposit area without a label. Clear guidelines for this specimen process should be created and processes audited to ensure compliance.

Technology can of course help with some of these issues. Using preprinted labels assures completeness and legibility. However, before a printed label is affixed to a sample, confirmation with the patient is still necessary. Barcode technology is another way of tracking samples and linking patients accurately to their samples.

Another key issue is that outpatient clinics and labs should have methods to capture these errors when they occur, even if only via a voluntary reporting system. This can allow tracking and trending of errors and further facilitate process redesign based on the types of errors identified. Only through aggressive error identification and subsequent action can we ensure a more error-free health care system in the future.

Tejal K. Gandhi, MD, MPH Director of Patient Safety Brigham and Women´s Hospital Boston, MA

References

1. Weingart SN, Wilson RM, Gibberd RW, Harrison B. Epidemiology of medical error. BMJ. 2000;320:774-7.[ go to PubMed ]

2. Gandhi TK, Weingart SN, Borus J, et al. Adverse drug events in ambulatory care. N Engl J Med. 2003;348:1556-64.[ go to PubMed ]

3. Gurwitz JH, Field TS, Harrold LR, et al. Incidence and preventability of adverse drug events among older persons in the ambulatory setting. JAMA. 2003;289:1107-16.[ go to PubMed ]

4. Moore C, Wisnivesky J, Williams S, McGinn T. Medical errors related to discontinuity of care from an inpatient to an outpatient setting. J Gen Intern Med. 2003;18:646-51.[ go to PubMed ]

5. Forster AJ, Murff HJ, Peterson JF, Gandhi TK, Bates DW. The incidence and severity of adverse events affecting patients after discharge from the hospital. Ann Intern Med. 2003;138:161-7.[ go to PubMed ]

6. Bonini P, Plebani M, Ceriotti F, Rubboli F. Errors in laboratory medicine. Clin Chem. 2002; 48:5:691-8.[ go to PubMed ]

7. Khoury M, Burnett L, Mackay MA. Error rates in Australian chemical pathology laboratories. Med J Aust. 1996;165:128-30.[ go to PubMed ]

8. Astion ML, Shojania KG, Hamill TR, Kim S, Ng VL. Classifying laboratory incident reports to identify problems that jeopardize patient safety. Am J Clin Pathol. 2003;120:18-26.[ go to PubMed ]

9. Nutting PA, Main DS, Fischer PM, et al. Toward optimal laboratory use. Problems in laboratory testing in primary care. JAMA. 1996;275:635-9.[ go to PubMed ]

10. Cullen DJ, Bates DW, Small SD, Cooper JB, Nemeskal AR, Leape LL. The incident reporting system does not detect adverse drug events: a problem for quality improvement. Jt Comm J Qual Improv. 1995;21:541-548.[ go to PubMed ]

11. McDermott RE, Mikulak RJ, Beauregard MR. The basics of FMEA. Portland, OR: Resource Engineering, Inc.; 1996.

12. Joint Commission on Accreditation of Healthcare Organizations. 2003 National Patient Safety Goals. [ go to related site ]