Tc-99m HIG Scintigraphy in Detection of Active Inflammation in Ankylosing Spondylitis

Abstract

Objective: The diagnosis of active inflammation in ankylosing spondylitis (AS) is crucial for treatment to delay possible persistent deformities. There are no specific laboratory tests and imaging methods to clarify the active disease. We evaluated the value of Tc-99m human immunoglobulin (HIG) scintigraphy in detection of active inflammation.

Material and methods: Twenty-nine patients were included. Tc-99m methylenediphosphonate bone (MDP) and HIG scintigraphies were performed within 2-5 day intervals. Two control groups were constituted both for MDP and HIG scintigraphies. Active inflammation was determined clinically and by serologic tests. Both scintigraphies were evaluated visually. Sacroiliac joint index values (SII) were calculated.

Results: Active inflammation was considered in five (sacroiliitis in 2, sacroiliitis-spinal inflammation in 1, achilles tendinitis in 1, arthritis of coxafemoral joints in 1) patients. HIG scintigraphy demonstrated active disease in all 3 patients with active sacroiliitis. But, it was negative in the rest. The other 2 active cases were HIG negative. Right and left SII obtained from HIG scintigraphy was higher (p<0.05) in clinically active patients than inactive patients. There was not any significant difference between patients with inactive sacroiliitis and normal controls. Right and left SII obtained from bone scintigraphy was higher (p<0.05) in patient group than in control group.

Conclusion: Clinically inactive AS patients, behave no differently than normal controls with quantitative sacroiliac joint evaluation on HIG scintigraphy. HIG scintigraphy may be valuable for evaluation of sacroiliac joints in patients with unc

Results: ertain laboratory and clinical findings.

Conflict of interest: None declared.

Keywords: Tc-99m-HIG; ankylosing spondylitis; inflammation.

Figure 1. Posterior static images of a control patient withphysiological HIG distribution (A: 4^th hour bone scan, B: blood poolHIG, C: 4^th hour HIG and D: 24^th hour HIG )

Figure 2. Posterior static images of a control patient withphysiological HIG distribution (A: 4^th hour bone scan, B: blood poolHIG, C: 4^th hour HIG and D: 24[ref:th]th[/ref] hour HIG )

Figure 3. A 32-y-old male with clinically active sacroiliitis. Flow (A),blood pool (B), 4^th hour planar (C) images of bone scan. CT (D), 4thhour (E) and 24^th hour (F) HIG images of pelvis. Note the increasedflow, hyperemia and osteoblastic activity in sacroiliac joints on bonescintigraphy (white arrows). Increased HIG accumulation andretention were concordant with the clinical findings in this patient.Degenerative changes of both sacroiliac joints accompanied withsubchondral sclerosis and small calcifications were reported on CT(white arrows). The bilateral gluteal uptake is due to the repeatedintramuscular injections (black arrows)

Figure 4. A 32-y-old male with the diagnosis of AS for 4 years. Thepatient was complaining of pain on the right knee. ESR and CRPwere found to be high but there was not active inflammation inclinical evaluation. Radiography (A), blood pool (B) and 4^th hour planarMDP (C) images, 4^th hour (D), 24^th hour HIG (E) images (bothanterior views). A marked hyperemia over the right knee joint andosteoblastic activity over patella, medial epicondyl, proximal tibia wasobserved on bone scan. HIG scan was similar to bone scan exceptthat the hyperemia and HIG accumulation on 4th hour images weremore prominent in lateral side of distal femur indicating a possibleinflammation of the tendon (arrows)