Pregnancy Inquiry at the Radiopharmacy Window
A 29-year-old woman arrives for a scheduled Tc-99m MDP bone scan for evaluation of low back pain. At the radiopharmacy window, the technologist asks standard screening questions. The patient reports her last menstrual period was 6 weeks ago and that her periods are usually regular, but she has not taken a pregnancy test. She says she "might be pregnant" but is not sure. The referring clinician's order does not mention pregnancy status. The prescribed activity is 740 MBq (20 mCi) Tc-99m MDP. The pharmacist is consulted about whether to proceed, delay, or modify the study.
1. How should the pharmacist frame the risk-benefit discussion, and what options should be presented to the patient and referring clinician?
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The pharmacist should treat this as an uncertain pregnancy status requiring a decision before administration, not as a routine scan.
Framing:
- Tc-99m MDP is excreted renally and localizes to bone; the fetal dose from a maternal 740 MBq MDP study is low (on the order of a few mGy), but the guiding principle is to avoid unnecessary fetal exposure when the indication is not urgent.
- The indication - low back pain - is generally not urgent, so the threshold for proceeding without confirming pregnancy status is high.
Options to present:
- Perform a pregnancy test first (urine or serum hCG). If negative, proceed as ordered.
- Delay the study until pregnancy status is confirmed, especially since the indication is non-urgent.
- If the study is clinically necessary despite possible pregnancy, discuss with the referring clinician and patient, document the conversation, and consider whether the information will change management.
- Optimize if proceeding: ensure adequate hydration and encourage voiding frequently after injection to reduce bladder/uterine exposure.
The decision belongs to the patient and referring clinician with the pharmacist providing accurate risk information; the pharmacist should not unilaterally cancel a clinically indicated study.
2. The patient declines a pregnancy test and says she wants the scan today. What should the pharmacist document and what practical instructions should be given?
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If the patient, after informed discussion, elects to proceed without a pregnancy test:
Documentation:
- That pregnancy status is unknown and the patient was informed of this.
- The risk-benefit discussion, including that the fetal dose is expected to be low but not zero.
- That the patient declined testing and wished to proceed, and that the referring clinician was notified (or the attempt to notify documented).
- The final administered activity and time.
Practical instructions:
- Hydrate well before and after injection.
- Void frequently for the first several hours after injection - a full bladder sits adjacent to the uterus and is a major contributor to fetal dose for renally excreted agents.
- Avoid prolonged bladder retention; do not delay voiding.
- Report any unexpected symptoms to the referring clinician.
The pharmacist should also flag the case so that the facility's policy on pregnancy screening (e.g., questioning and testing thresholds for patients of childbearing age) can be reviewed if the order failed to capture pregnancy status.