You have been studying the radioactive specimens sent to your laboratory. What got you interested in this topic?
A: In the fall of 2019, our hospital core laboratory unexpectedly received specimens labeled as radioactive from a patient who was receiving an experimental radiopharmaceutical treatment. At that time, our laboratory was unprepared to handle radioactive specimens. In addition, because the laboratory did not perform radioimmunoassays, personnel had not received radiation safety training. This event led to an investigation of all radioactive specimens received in the laboratory.
Why are some patient specimens radioactive?
Major medical centers and cancer centers use numerous types of radiopharmaceuticals routinely for both diagnosis (generally lower doses) and treatment (generally higher doses). Ideally, patients receiving high doses of radiopharmaceuticals should have specimens drawn for laboratory testing prior to administration, but this is not always possible.
What types of radioactive materials are sent to your laboratory?
Over a nearly 2-year period, we calculated that over 11,000 patient blood, urine, stool, and other body fluid specimens were sent to our laboratory within 5 physical half-lives of nine different radionuclides being administered. The radionuclides primarily consisted of beta and gamma emitters. Beta particles have localized effects, and their ability to damage tissue allows them to be effective antineoplastic agents. However, thin materials such as plastic typically block them. Therefore, beta particles pose a greater risk to people from sources inside and on the surface of the body than from sources outside the body. In contrast, gamma rays can travel great distances and have the ability to penetrate materials that would block other radioactive particles. Therefore, gamma rays pose a risk to people even from sources outside the body.
Do you think this radioactivity poses a threat to laboratory employees?
Overall, our study demonstrated that laboratory staff are at low risk of incurring a harmful exposure from most of the samples received in our lab. Risk is difficult to truly assess, though. It depends on the radionuclide, how radiopharmaceuticals distribute in the body, the time between sample collection and receipt in the laboratory, and how specimens are handled. For instance, we found that if specimens are held at the top of the tube, no specimens can deliver a 2 mrem effective dose of gamma radiation in <5 minutes. However, if specimens are held firmly in the palm of the hand, many specimens could potentially deliver this dose in <2 minutes.
Furthermore, the index specimens that were sent to our laboratory labeled as radioactive had over 30 microCuries of iodine-131. This means these specimens contained enough radioactivity to exceed our institutional threshold and would have been considered a “major spill” if they were dropped in the lab. Specimens such as these present a real risk to laboratory personnel and need to be handled with extra caution and disposed of properly.
What recommendations do you have for laboratories regarding radioactive specimens?
We recommend that laboratories do the following: 1) Provide radiation safety training for all personnel. 2) Maintain open lines of communication with members of radiation safety and radiation oncology. This enables labs to stay informed about when they will get samples from patients who have received high doses of radiopharmaceuticals. 3) Develop protocols for the labeling and transport of specimens with significant radioactivity. 4) Develop protocols for tracking the receipt, processing, and disposal of specimens from patients who received large doses of radiopharmaceuticals. 5) Assess cumulative exposure to personnel and instruments with dosimeters. 6) Assess for potential environmental contamination with periodic wipe testing. 7) When possible, collect patient specimens before radioisotope administration or after at least 5 physical half-lives.
Christopher G. Suciu, MD, is a consulting pathologist at Washington University School of Medicine in St. Louis. +Email: [email protected]
The author thanks his Washington University colleagues Ann M. Gronowski, PhD, and Max Amurao, PhD, for their support investigating radioactivity in the clinical laboratory.