Nucleographic studies of axial spondarthritides. I. Quantitative sacroiliac scintigraphy in early HLA-B27-associated sacroiliitis.

Abstract

AbstractQuantitative sacroiliac scintigraphy (QSS) was performed on 34 patients suspected of having ankylosing spondylitis (AS) with low back pain and stiffness of recent onset, by utilizing three technical features not previously described: fractional scintigraphy of the sacroiliac (SI) joints, background subtraction, and drug washout. Imaging was performed with a 140‐keV, high‐resolution collimator, and the data were recorded and processed with an Ohio Nuclear 150 System, 3 hours after administration of 17 mCi of 99m Tc ethane‐1‐hydroxy‐1, 1‐diphosphonate (EHDP) per 70 kg of body weight. The SI index determined by QSS was compared with diagnostic tissue‐typing for HLA–B27 and standard radiography of the SI joints to assess the potential of QSS to discriminate inflammatory sacroiliitis from nonspecific low back strain. Twenty‐three of the 34 patients were positive for HLA–B27 and they had a mean index by QSS of 2.09. All but 1 had an index exceeding 1.7. Only 5 of these B27‐positive patients had early radiographic sacroiliitis. The 11 B27‐negative patients had a mean index by QSS of 1.52, and none had radiographic sacroiliitis. The mean values for 46 controls and 10 patients with classic AS, B27 positivity, and complete sclerosis of their SI joints were 1.32 and 1.38, respectively, suggesting that the elevated SI indices found by QSS in the symptomatic B27‐positive patients do reflect inflammatory sacroiliitis. Five of the recently symptomatic B27‐positive patients with elevated indices had repeat QSS after 3 weeks of therapy with conventional antiin‐flammatory drugs and had a reduction in their SI index. QSS appears to be useful in detecting inflammatory sacroiliitis associated with B27 positivity before the development of radiographic disease, and it may be an objective tool in assessing the short‐term therapy of inflammatory sacroiliitis.