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Home , Scintigraphy

SUMMARY TABLE

Table 1: Summary of Criterion Evidence Domain 1: Criteria Related to the Underlying Health Condition Criterion Synthesized Information 1 Size of the affected The annual incidence of hospitalization (considered an estimation of incidence) for LGIB has been population estimated to be 20 to 30 per 100,000 persons in the US.1,7,8,12,13,29 Assuming the incidence rate in Canada is similar to that of the US, this corresponds to more than 1 in

10,000 (0.01%) and less than or equal to 1 in 1,000 (0.1%). 2 Timeliness and The timely detection and accurate localization of bleeding sites are essential for the guidance of urgency of test treatment in high-risk patients.2,9,11,19 results in planning According to the Saskatchewan hospital guidelines, scans for detection of acute GI bleeding patient management should be performed within 24 hours of the request (Patrick Au, Acute and Emergency Services Branch, Saskatchewan Ministry of Health: unpublished data, 2011). Test results have a significant impact on the management of the condition or the effective use of heath care resources.

3 Impact of not Mortality is reported in 2% to 4% of patients with LGIB.1,3,13 Early diagnosis of patients with severe performing a bleeding, and early therapeutic interventions, lead to lower mortality rates.13 diagnostic imaging Diagnostic imaging results can have minimal impact on mortality. test on mortality related to the underlying condition 4 Impact of not No studies investigating the impact of scintigraphy or on health outcomes or quality of life in performing a patients with LGIB were identified, although between 5% and 50% of patients with persistent LGIB diagnostic imaging require surgical interventions.7 Failure to diagnose and treat chronic LGIB results in chronic anemia, test on morbidity or which does affect quality of life and also can cause anxiety (MIIMAC expert opinion). quality of life related Diagnostic imaging results can have moderate impact on morbidity or quality of life. to the underlying condition

Domain 2: Criteria Comparing 99mTc with an Alternative or Comparing Between Clinical Uses Criterion Synthesized Information 5 Relative impact on To be scored locally.

health disparities 6 Relative acceptability GI Scintigraphy: Patients may have concerns about radiation exposure and the intravenous injection of a of the test to patients agent. Abdominal angiography: Patients undergoing X-ray angiography may have concerns over radiation exposure and injection of contrast material. 99mTc-GI scintigraphy is significantly more acceptable to patients than abdominal angiography.

7 Relative diagnostic No studies comparing the diagnostic accuracy of scintigraphy to CT-angiography or MR-angiography accuracy of the test were identified. The included systematic review reported a pooled sensitivity rate of 62% for scintigraphy.18 There was a noticeable heterogeneity between the seven included primary studies,19-25 regarding patient population, scintigraphy techniques, and reference standard. No studies comparing the diagnostic accuracy of scintigraphy to CT-angiography or MR-angiography were identified.

Diagnostic Accuracy

Test Reference Type of Evidence Sensitivity (%) Specificity (%)

99mTc-scan Abdominal angiography SR and Obs 50.0 to 79.0 30.0 to 66.7

Abdominal Surgery/clinical follow- angiography up Non-SR review 40.0 to 86.0 NA NA = not available; Obs = observational studies; SR = systematic review; 99mTc = -99m. tests can be performed over a longer observation period, thus increasing the likelihood that bleeding will be present at the time of testing (MIIMAC expert opinion). Overall, the diagnostic accuracy of 99mTc-based scintigraphy is significantly better than abdominal angiography.

Domain 2: Criteria Comparing 99mTc with an Alternative or Comparing Between Clinical Uses Criterion Synthesized Information 8 Relative risks Non–radiation-related Risks associated with the 99mTc-scintigraphy for GI bleeding: 99mTc-scintigraphy is non-invasive and associated with no morbidities test or mortalities.2,22 On rare occasions, allergic reactions to used for scintigraphy may occur.12,32 Abdominal Angiography: This is an invasive procedure, with a potential for major complications, particularly in the elderly and in patients with comorbid illness.12,28 AEs are reported in 0% to 26% of patients undergoing angiography.2,7,28 The most common complication is hematoma or bleeding at the catheter site.7 Other potential AEs include arterial dissection, catheter site infection, loss of pulses in the lower extremity, and allergic reactions to the contrast agent.2,7,12,28 More contrast is needed for the imaging of LGIB than for many other tests (MIIMAC expert opinion). Radiation-related Risks Both abdominal scintigraphy and angiography expose the patient to . The average radiation exposure is higher for angiography than for GI bleeding scintigraphy.33

Average Effective Doses of Radiation Procedure Average Effective Dose (mSv) GI scintigraphy 7.833 Abdominal angiography 1233 Average background dose of radiation per year 1 to 3.034-36 GI = gastrointestinal; mSv = millisievert. 99mTc-based GI scintigraphy is significantly safer than abdominal angiography.

9 Relative availability of As of 2006 in Canada, there were 2,034 diagnostic radiologists, 221 nuclear medicine physicians, 12,255 personnel with radiological technologists, and 1,781 nuclear medicine technologists. Yukon, Northwest Territories, and expertise and Nunavut did not have the available personnel to perform and interpret tests to image lower GI bleeding. experience required Other jurisdictions (e.g., Prince Edward Island) may offer limited nuclear medicine services. for the test Overall, the availability of health professionals to evaluate LGIB is good; however, a specialized centre to perform abdominal angiography may be required.

Domain 2: Criteria Comparing 99mTc with an Alternative or Comparing Between Clinical Uses Criterion Synthesized Information Assuming the equipment is available, if GI scintigraphy using 99mTc-radiolabelled isotopes is not available, it is estimated that 25% to 74% of the procedures can be performed in a timely manner using

abdominal angiography. 10 Accessibility of Equipment: As of January 1, 2007, there was an average of 18.4 nuclear medicine cameras per million alternative tests people, with none available in the Yukon, Northwest Territories, or Nunavut.32 There were 179 (equipment and wait angiography suites for an average of 5.5 suites per million people.37 times) Wait times: In 2007, the latest year for which data are available, the average time for nuclear medicine examinations at MUHC hospitals was five days. However, the wait times were reported to be less than one day for emergency cases.38 In the same year, wait times of angiography procedures at MUHC hospitals were 21 days in general, and less than 12 hours for emergency and urgent cases.38 A specialized centre may be required to perform abdominal angiography. Assuming the necessary expertise is available, it is estimated that between 25% to 74% of procedures can be performed in a timely manner using abdominal angiography. 11 Relative cost of the According to our estimates, the cost of 99mTc-labelled RBC scintigraphy is $239.80. Abdominal test angiography is a significantly more costly alternative. Relative Costs Test Total Costs ($) Cost of Test Relative to 99mTc-based Test ($) RBC scintigraphy 239.80 Reference Abdominal angiography 898.86 659.06

AE = adverse event; CT = computed ; GI = gastrointestinal; LGIB = lower gastrointestinal bleed; MIIMAC = Medical Isotopes and Imaging Modalities Advisory Committee; MR = magnetic resonance; MUHC = McGill University Health Centre; RBC = red blood cells; 99mTc = technetium-99m; US = United States.