Diagnostic value of quantitative sacroiliac joint scintigraphy in brucellosis

Increased bone activity in the sacroiliac joints has been shown to be a sensitive method for detecting sacroiliitis in brucellosis. Because symmetrically increased uptake usually is difficult to detect, this study was performed to improve the sensitivity by quantifying sacroiliac joint uptake. Quantification was accomplished by normalizing sacroiliac joint activity to activity in the lumbar spine and sacrum. From rectangular regions of interest over a standardized posterior pelvic view, the ratios of the sacroiliac:lumbar spine and sacroiliac:sacrum were calculated. Abnormal sacroiliac joint uptake was defined as uptake greater than the mean +2 SD of normal. This was applied to 79 patients with brucella sacroiliitis. The quantitative approach was compared with visual interpretation. Of the 16 patients in the age group of 5 to 19 years, 7 patients had visual evidence of sacroiliitis and 9 patients had positive evidence by sacroiliac-sacrum and 12 by sacroiliac-lumbar spine quantification. Of 21 patients who were 20 to 30 years old, 10 patients had positive visual evidence, whereas 17 and 20 patients had positive evidence of sacroiliitis by sacroiliac-sacrum and sacroiliac-lumbar spine, respectively. Of 42 patients who were 31 to 85 years old, 24, 32, and 36 patients had positive evidence of sacroiliitis by visual inspection, sacroiliac-sacrum, and sacroiliac-lumbar spine, respectively. Thus, the quantitative approach increased the sensitivity in diagnosing Brucella sacroiliitis in all age groups by 31.3%, 47.6%, and 28.6%, respectively, for sacroiliac-lumbar spine and by 12.5%, 33.3%, and 19%, respectively, for sacroiliac-sacrum.