The technologist is responding to a stat urinalysis request on a patient in the Emergency Unit with abdominal pain. The technologist observes a positive finding for blood. The emergency physician vehemently insists that the result is incorrect. The urinalysis blood test is negative in their hands. The technologist repeats the results and gets the same positive answer.
- What are the possible reasons, or sources of error, for the discrepant results?
- The technologist checks for mislabeling and finds this has not obviously occurred. The laboratory specimen does not appear grossly contaminated. The technologist opens a new batch of test urine dipsticks and gets the same answer. The technologist calls the physician back and asks how the ER determined that the patient’s urine was negative for blood; the answer is that they have urine dipsticks and performed their own test. What possible errors can occur when performing urine dipstick testing?
- What are some of the ways to resolve this dispute?
The supervisor went down to the Emergency Room to investigate how testing was being performed there. This ER physician was performing tests in an unsanctioned manner. The strips were 3 years out of date and were found in an un-capped storage container, exposed to the air. When the ER physician repeated the urine analysis with fresh strips; the results were the same as those obtained by the technologist. The ER physician was satisfied with the laboratory’s resolution of the problem and discarded the outdated strips. The laboratory took steps to place this type of testing under the umbrella of Point-of-Care Testing (POCT) that is controlled by the central laboratory. See Chapter 17, especially pages 308-309.
- There are several possible reasons: Specimen mix-up (that is, mislabeling of samples), contamination, or error of analysis by either the ER Physician or the laboratory technologist.
- The reagents incorporated into the dipstick’s reaction pads can deteriorate if the strips are not properly stored in a dry, relatively cool place. The deterioration is time dependent, and so the strips can only be used within the expiration dates indicated on the container (manufacturer’s and post-opening of the reagent bottle). Also, each test on the tesat strip must be properly timed for optimal results. Performing QC on a regular basis can validate both the strips and technique. See Chapter 57 and Urinalysis Infobase on the CD-ROM.
- The laboratory POCT supervisor needs to visit the ER and see how the testing is being performed. The expiration date on the ER team’s test strips needs to be verified as well as the manner of storage. In addition, the supervisor can take the patient’s specimen and a fresh set of test strips to the ER and ask that the ER test the urine with both the lab’s and the ER’s strips.