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

Abstract

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. 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. In this study, we employed the in-house 99mTc-HSA preparation to study GI protein loss in two patients. Not applicable. 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. 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. 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.