Systematic review and meta-analysis comparing the diagnostic utility of Tc-99m tagged RBC scintigraphy with CT-angiography imaging studies in diagnosing lower gastrointestinal bleeding

Background@#Lower Gastrointestinal bleeding (LGIB) is a serious and urgent condition which can be assessed using several different modalities. Tc-99m tagged RBC scintigraphy has been established as a diagnostic tool in Nuclear Medicine but several other modalities, including CT-based imaging (i.e. angiography) currently exist. @*Objective@#The objective of this study is to compare Tc-99m tagged RBC scintigraphy with CT-based imaging studies in terms of clinical utility and diagnostic outcomes. @*Methods@#A systematic review of available literature was done, with the goal of creating a meta-analysis focusing on the reported diagnostic outcomes - mainly sensitivity and specificity on the presence of a LGIB. Aside from this, a systematic review of the clinical utility and the differences of each test were discussed, including non-quantifiable advantages. The literature search was conducted following the guidelines of PRISMA, with searches from PubMed, Medline, and other pertinent databases. Quality assurance was done using the QUADAS tool. Statistical analyses of sensitivity, specificity, and a summary receiver operating characteristics plot were computed for the meta-analysis.@*Results@#Pooled sensitivity and specificity for RBC scintigraphy were 0.886 and 0.119, respectively. Pooled sensitivity and specificity for CT-based imaging were 0.729 and 0.660, respectively. CT based imaging also showed higher localization and faster completion times. RBC scintigraphy had a longer acquisition window.@*Conclusion@#Both Tc99m-tagged RBC scintigraphy and CT-based imaging have important clinical utility, with each modality having different advantages that the other test cannot provide.

Comparison of Fixed versus Calculated Activity of Radioiodine for the Treatment of Graves Disease in Adults

BACKGROUND: Radioactive iodine as a treatment modality has been shown in several studies to be a safe and effective therapy for Graves disease. However, there is still no uniformity regarding optimal dosing method. The aim of this study is to compare the efficacy of calculated and fixed dosing of radioiodine for the treatment of Graves disease. METHODS: A hundred twenty-two patients diagnosed with Graves disease were randomized to receive either fixed or calculated dose of radioiodine. Those randomized to fixed activity received either low fixed activity at 9.9 mCi for thyroid gland size <40 g or high fixed activity at 14.9 mCi for thyroid gland size 40 to 80 g, and those grouped to calculated activity received 160 µCi/g of thyroid tissue adjusted for 24 hours radioiodine uptake. Thyroid function tests (free thyroxine [T4] and thyroid stimulating hormone [TSH]) were monitored at 10, 16, and 24 weeks after radioactive iodine therapy. The primary outcome, treatment failure was defined as persistently elevated free T4 and low TSH. RESULTS: Of the 122 patients randomized, 56 in the fixed dose group and 56 in the calculated dose group completed the follow-up. At the end of 6 months, the percentage of treatment failure was 37.50% in the calculated dose group versus 19.64% in the fixed dose group with a relative risk of 0.53 (95% confidence interval, 0.28 to 0.98) favoring the fixed dose group. CONCLUSION: Fixed dose radioiodine has a significantly lower incidence of persistent hyperthyroidism at 6 months post-radioactive therapy.