In-house preparation of technetium 99m-labeled human serum albumin for evaluation of protein-losing gastroenteropathy

OBJECTIVE: To develop an in-house preparation method for technetium 99m-labeled human serum albumin (99mTc-HSA) to meet the clinical need for gastrointestinal (GI) protein loss evaluation in our institution. DESIGN/SETTING: Our in-house HSA was prepared by slowly adding 2 mL of 25% HSA to 50 mL nitrogen-purged, sterilized water. We then continued the nitrogen purging process for another 15 minutes before adding 0.5 mL of stannous chloride (SnCl2) in concentrated hydrochloride (40 mg/mL) to the HSA solution. Next, we transferred 1 mL of the mixture to a 5 mL vial containing 0.5 mL of 30 mCi (1,110 MBq) 99mTc. Using a paper chromatography method during a 6-hour postpreparation time period, we evaluated the effects of filtration (0.2 microm membrane filter versus no filtration) and storage temperature (25 degrees C versus 37 degrees C) on the in vitro stability of 99mTc-HSA. PATIENTS OR OTHER PARTICIPANTS: In this study, we employed the in-house 99mTc-HSA preparation to study GI protein loss in two patients. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: We used a radiochemical purity (RCP) value of not less than 90% as the index for determining in vitro stability of the in-house 99mTc-HSA preparation. The nuclear medicine physician interpreted the image to determine the location and extent of protein loss in the GI tract. RESULTS: Our results demonstrate that the overall RCP of 99mTc-HSA was 95.0% +/- 2.2% (mean +/- SD). We found no statistically significant difference in RCP value between filtered and nonfiltered 99mTc-HSA preparations across the sampled time points. However, RCP values tended to increase with time for each of the temperature-controlled preparations (P < .01). Storage temperature had a significant effect (P < .01), with refrigerated samples having an estimated 2.2% lower RCP value across time. However, the difference between room temperature and refrigerated samples decreased over time (P < .02) to only 1.1% at the 6-hour sampling. We noted gradual accumulation of 99mTc-HSA within the first hour in one patient, and the imaging results indicate that both patients had protein-losing enteropathy. CONCLUSION: It is relatively easy to prepare 99mTc-HSA in-house, achieving a high RCP level as well as extended in vitro stability. The clinical data further indicate that our in-house preparation of 99mTc-HSA may be useful for the study of GI protein loss; however, further clinical evaluation is needed.