SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY IN THE DIAGNOSIS OF INFLAMMATORY SPONDYLOARTHROPATHIES

Objective. The role of bone scintigraphy in the evaluation of patients with inflammatory spondyloarthropathy is controversial and previous s tudies have reported a lack of sensitivity and specificity. The aim of our study was to determine whether single photon emission computed to mography (SPECT) scanning would enhance the clinical utility of bone s cintigraphy in the detection of inflammatory axial disease, in particu lar sacroiliitis. Methods. Twenty patients with definite sacroiliitis (New York criteria >1) on plain film radiographs and 20 age matched co ntrols were studied. Bone scintigraphy and SPECT scanning were carried out 2 h after an intravenous injection of Tc-99m imidodiphosphonate ( IDP). A quantitative and qualitative assessment of radiopharmaceutical uptake in the sacroiliac (SI) joints was derived from planar films an d a qualitative analysis of uptake in the SI joints was derived from S PECT scans. All films were read without knowledge of patient identific ation. Results. Quantitative analysis of planar films did not identify any difference between study and control groups (p>0.05). Qualitative assessment of planar films identified features of!sacroiliitis more f requently in patients than in controls (p<0.05) with a sensitivity of 25% and a specificity of 95%. SPECT scanning also revealed enhanced ra diopharmaceutical uptake in the SI joints more frequently in patients than in controls (p<0.001) with a sensitivity of 85% and a specificity of 90%. Increased uptake in the lumbar facet joints and costovertebra l joints was identified in 3 patients. Similar abnormalities were not detected in the control group. Conclusion. Our results indicate that S PECT scanning is both sensitive and specific for the detection of esta blished sacroiliitis and may also identify inflammatory disease at oth er sites in the spine.