Sensitivity and specificity of magnetic resonance imaging for axial spondyloarthritis

Diagnosing spondyloarthritis (SpA) early in young patients with inflammatory back pain and normal findings on radiographs of the sacroiliac joints (SIJ) remains a challenge in routine practice. Magnetic resonance imaging (MRI) is regarded as the most sensitive imaging modality for detecting early SpA before the radiographic appearance of structural lesions. The recently published Assessment of SpondyloArthritis International Society classification criteria for axial SpA include for the first time a positive MRI demonstrating sacroiliitis as an imaging criterion indicative of SpA together with at least 1 clinical feature of SpA. A systematic and standardized evaluation of the SIJ in patients with SpA showed that MRI has much greater diagnostic utility than documented previously and allowed a data-driven definition of a positive MRI for SpA. Single MRI lesions suggestive of inflammation can be found in the SIJ and the spine in up to one quarter of healthy controls and young patients with mechanical back pain.     

High frequency of inflammatory back pain and other features of spondyloarthritis in patients with rheumatoid arthritis

The aim of this study was to investigate the frequency of patients with rheumatoid arthritis (RA) who have inflammatory back pain (IBP) and meet the existing classification criteria for ankylosing spondylitis (AS) and spondyloarthritis (SpA). We included 167 patients fulfilling the ACR 1987 revised criteria for RA. After obtaining a medical history and performing a physical examination, standard pelvic X-rays for examination of the sacroiliac joints (SIJ) were ordered in all patients. A computed tomography (CT) or magnetic resonance imaging (MRI) of SIJ was performed in patients with suspected radiographic sacroiliitis and MRI of SIJ in those who have IBP but no radiographic sacroiliitis. IBP was defined according to both Calin and experts’ criteria. The modified New York (mNY) criteria were used to classify AS, both ESSG and Amor criteria for SpA and ASAS classification criteria for axial SpA. There were 135 female and 32 male patients with a mean age of 54.8 years. The mean disease duration was 9.8 years. RF was positive in 128 patients (79.2 %) and anti-CCP in 120 patients (81.1 %). Twenty-eight patients with RA (16.8 %) had IBP (Calin criteria), and four (2.4 %) had radiographic sacroiliitis of bilateral grade 3. Three patients (1.8 %) fulfilled the mNY criteria for AS, 31 (18.6 %) ESSG and 26 (15.6 %) Amor criteria for SpA. Nine patients (five with MRI sacroiliitis) (5.3 %) were classified as having axial SpA according to new ASAS classification criteria. This study suggests that the prevalence of SpA features in patients with RA may be much higher than expected.     

How should we diagnose spondyloarthritis according to the ASAS classification criteria: a guide for practicing physicians

The Assessment of SpondyloArthritis International Society (ASAS) group has recently developed criteria to classify patients with axial SpA with or without radiographic sacroiliitis, and criteria to classify patients with peripheral SpA. The ASAS axial criteria consist of 2 arms and can be applied in patients with back pain (>3 months almost every day). In one arm, imaging (radiographs and magnetic resonance imaging [MRI]) has an important role, in the other arm--HLA-B27. MRI can detect active inflammation and structural damage associated with SpA. According to the ASAS axial SpA criteria, patients with chronic back pain aged less than 45 years at onset can be classified as having axial SpA if sacroiliitis on imaging (radiographs or MRI) plus 1 further SpA feature are present, or if HLA-B27 plus 2 further SpA features are present. The ASAS peripheral criteria can be applied in patients with peripheral arthritis (usually asymmetric arthritis predominantly involving the lower limbs), enthesitis, or dactylitis. Patients can be classified as having peripheral SpA if 1 of the following features is present: uveitis, HLA-B27, preceding genitourinary or gastrointestinal infection, psoriasis, inflammatory bowel disease, sacroiliitis on imaging (radiographs or MRI), or if 2 of the following features besides the entry feature are present: arthritis, enthesitis, dactylitis, inflammatory back pain, or a positive family history of SpA.     

Atlas of MRI findings of sacroiliitis in pediatric sacroiliac joints to accompany the updated preliminary OMERACT pediatric JAMRIS (Juvenile Idiopathic Arthritis MRI Score) scoring system: Part II: Structural damage lesions

Magnetic resonance imaging (MRI) is the imaging modality of choice for identifying sacroiliitis in juvenile idiopathic arthritis (JIA). Besides active lesions of sacroiliitis, of which bone marrow edema (BME) is the key feature, structural damage lesions can also be detected. Structural changes include erosion, sclerosis, fat lesion, backfill and ankylosis, and are more common at later stages. Systematic MRI assessment of inflammation and structural damage may aid in monitoring the course of the disease and evaluating treatment options. In this pictorial essay, we illustrate normal MRI findings and growth-related changes of the SIJ in the pediatric population, as well as the different MRI features of structural damage of sacroiliitis. This atlas can serve as a reference for assessing structural lesions of SIJ arthritis according to the updated preliminary JAMRIS (Juvenile Idiopathic Arthritis MRI Score) scoring system proposed by the MRI in JIA working group of Outcome Measures in Rheumatology and Clinical Trials (OMERACT). The atlas is intended to be read in conjunction with its companion Part 1, Active Lesions.     

Local infliximab injection of sacroiliac joints in non-radiographic axial spondyloarthritis: Impact on clinical and magnetic resonance imaging parameters of disease activity

Abstract

Objectives. To evaluate the effectiveness of infliximab (IFX) injection into sacroiliac joints (SIJs) of non-radiographic axial spondyloarthritis (nr-axial SpA) and its impact on clinical and MRI parameters of disease activity.

Methods. Thirty-seven patients fulfilling the Association of Spondyloarthritis International Society (ASAS) criteria for axial SpA were initially studied, with disease duration not exceeding 1 year and failed to respond to non-steroidal anti-inflammatory drugs (NSAIDs). Only SpA having active sacroiliitis on MRI without spondylitis (number = 7) were selected to receive bilateral SIJ injection of 20 mg IFX. Follow-up MRI was done at 24 weeks post-injection. Patients were clinically evaluated before, and 12 and 24 weeks after SIJ injection. Evaluation included back pain and stiffness scores, and Bath Ankylosing Spondylitis (BAS) Disease indices and C-reactive protein (CRP) levels. ASAS response criteria were also assessed.

Results. Twelve and twenty-four weeks after injection, there was significant decrease in back pain, stiffness, and BAS Disease Activity and Global indices. BAS Functional index, CRP, and mean bone marrow edema score of SIJs were decreased without reaching statistical significance. All patients achieved ASAS20 and five (71.4%) achieved ASAS40.

Conclusion. SIJ injection of IFX could be a therapeutic option in early nr-axial SpA who failed to respond to NSAIDs.     

The influence of patient characteristics, disease variables, and HLA alleles on the development of radiographically evident sacroiliitis in juvenile idiopathic arthritis

OBJECTIVE: To assess the frequency of sacroiliitis and the radiographic and clinical outcome in juvenile idiopathic arthritis (JIA) and determine patient characteristics, early disease variables, and genetic markers that predict development of sacroiliitis. METHODS: We performed a retrospective cohort study of 314 (79%) of the 400 JIA patients first admitted to the hospital between 1980 and 1985. The participants were examined after a median disease duration of 14.9 years (range 11.7-25.1). Radiographs of the sacroiliac joints, hips, ankles, and tarsi were obtained and studied in a blinded manner by 2 radiologists. The presence of HLA-DRB1 and DPB1 alleles was determined by genotyping and that of HLA-B27 by serologic testing. Variables relating to the onset and course of the disease were obtained by chart reviews. RESULTS: Twenty (6%) of the JIA patients developed radiographic sacroiliitis according to the New York criteria. In 9 patients (45%), sacroiliitis had not been demonstrated before the followup examination. At followup, spinal flexion (lateral and anterior) was reduced in 70-75% of patients with sacroiliitis and in 30-35% of those without sacroiliitis. Compared with the JIA patients without sacroiliitis, those with sacroiliitis more frequently had inflammatory back pain, enthesitis, radiographic changes in the hips and calcanei, erosions of any peripheral joint, and uveitis. Predictors of sacroiliitis were HLA-B27, absence of DPB1*02, hip joint involvement within the first 6 months, and disease onset after age 8 years. The following factors were more common among patients in whom sacroiliitis developed than in other JIA patients: DRB1*04, male sex, family history of ankylosing spondylitis, psoriasis, inflammatory back pain, and enthesitis within the first 6 months. CONCLUSION: In the current study, radiographically evident sacroiliitis had developed in 6% of JIA patients after a median disease duration of 14.9 years. HLA-B27, absence of DPB1*02, late onset of disease, and early hip involvement were predictors of sacroiliitis.     

Prospective evaluation of sacroiliac scintigraphy in chronic inflammatory back pain

To assess the usefulness in screening for sacroiliitis of a wide band profile cut which included the entire sacroiliac (SI) joint, 34 patients with chronic inflammatory back pain (IBP) underwent sacroiliac joint scintigraphy with ^99mTc-methylene diphosphonate while receiving no antiinflammatory therapy. The sacroiliac joint to sacrum (SIJ/S) ratios in those with back pain differed significantly from the ratios of an age-matched control group. However, 12 of the 34 patients with inflammatory back pain had normal or equivocal sacroiliac radiographs and 4 of 12 had normal SIJ/S ratios. All 4 were HLA-B27 positive, had diminished lumbar movement, and required antiinflammatory medication; 2 had diminished chest expansion; 1 has developed iritis. We conclude that this technique is not a reliable screening procedure. Therapy with antiinflammatory drugs was associated with a significant decrease in the SIJ/S ratios in 19 of the 34 who were reimaged.     

Low grade radiographic sacroiliitis as prognostic factor in patients with undifferentiated spondyloarthritis fulfilling diagnostic criteria for ankylosing spondylitis throughout follow up

OBJECTIVE: To determine the rate and factors associated with ankylosing spondylitis in a cohort of patients with undifferentiated spondyloarthritides (SpA). METHODS: 62 consecutive patients with undifferentiated SpA seen between 1998 and 1999 underwent clinical and imaging evaluations throughout follow up. The main outcome measure was a diagnosis of ankylosing spondylitis. RESULTS: 50 patients with peripheral arthritis (n = 35) and inflammatory back pain (n = 24) (26 male; mean (SD) age at onset, 20.4 (8.8) years; disease duration 5.4 (5.7) years) were followed up for 3-5 years. At baseline, >90% of patients had axial and peripheral disease, while 38% had radiographic sacroiliitis below the cut off level for a diagnosis of ankylosing spondylitis (BASDAI 3.9, BASFI 2.9). At the most recent evaluation, 21 patients (42%) had ankylosing spondylitis. Two factors were associated with a diagnosis of ankylosing spondylitis in multivariate analysis: radiographic sacroiliitis grade <2 bilateral, or grade <3 unilateral (odds ratio (OR) = 11.18 (95% confidence interval, 2.59 to 48.16), p = 0.001), particularly grade 1 bilateral (OR = 12.58 (1.33 to 119.09), p = 0.027), and previous uveitis (OR = 19.25 (1.72 to 214.39), p = 0.001). Acute phase reactant levels, juvenile onset, and HLA-B27 showed a trend to linkage with ankylosing spondylitis (NS). CONCLUSIONS: Low grade radiographic sacroiliitis is a prognostic factor for ankylosing spondylitis in patients originally classified as having undifferentiated SpA. Low grade radiographic sacroiliitis should be regarded as indicative of early ankylosing spondylitis in patients with undifferentiated SpA.     

Evaluation of acute and chronic MRI features of sacroiliitis in asymptomatic primary hyperparathyroid patients

Asymptomatic primary hyperparathyroidism (PHPT) is characterized with autonomous overproduction of parathyroid hormone without signs or symptoms associated with hyperparathyroidism. Before symptoms become obvious, PHPT may affect structures like sacroiliac joints, which consist of bone. So, in the asymptomatic PHPT patients, structural and inflammatory changes in sacroiliac joints may lead to confusion during diagnosis workup of axial spondyloarthropathy. In this study, we evaluated active and chronic sacroiliac magnetic resonance imaging (MRI) changes relevant to sacroiliitis in the patients with asymptomatic PHPT and interpreted bone marrow edema within the scope of Assessment of SpondyloArthritis International Society–Outcome Measures in Rheumatology Clinical Trials (ASAS-OMERACT) criteria. Forty-nine patients with asymptomatic PHPT, 26 patients with newly diagnosed axial spondyloarthropathy (SpA), and 37 healthy controls were enrolled. All subjects were evaluated by sacroiliac MRI for four active (bone marrow edema, enthesitis, capsulitis, and synovitis) and four chronic (subchondral sclerosis, subchondral/periarticular erosions, periarticular fat deposition, and bony bridges/ankylosis) lesions relevant to sacroiliitis. Bone marrow edema compatible with ASAS-OMERACT active sacroiliitis criteria in sacroiliac MRI was fulfilled by 16.3 % (8/49) of the asymptomatic PHPT patients which was similar with controls but statistically lower than axial SpA. Moreover, asymptomatic PHPT patients and controls were similar for other chronic or active MRI findings. Also, we detected lower frequency of all other MRI findings, except enthesis, in asymptomatic PHPT patients according to axial SpA. Acute inflammatory including bone marrow edema fulfilling ASAS-OMERACT active sacroiliitis criteria and chronic structural sacroiliac lesions relevant to sacroiliitis in MRI were detected in asymptomatic PHPT similar frequency with controls but as expected, lower than axial SpA. But, these findings could not be attributed to excessive secretion of parathyroid hormone.     

Sacroiliac joints: osteoarthritis or arthritis

One of the most challenging aspects of treating the sacroiliac joint (SIJ) pain is the complexity of diagnosis. Imaging methods have gained importance for the diagnosis of SIJ diseases. CT and MR exams had equal efficacy superior to radiography in staging structural changes in the SIJ due to osteoarthritis or sacroiliitis. The diagnosis of spondyloarthropaty can be delayed for several years using certain radiography studies. MR imaging reveal early cartilage changes and active inflammatory changes in the subchondral bone and surrounding ligaments in spondyloarthropaties, as well as subperiosteal and transcapsular yuxtaarticular infiltrations characteristic of septic sacroiliitis, which could not be found by either CT of radiography. T1-WI with fat suppression (FS) and STIR images improve the demonstration of erosions and inflammatory changes respectively, on MR studies. Additional T1-FS after i.v. contrast has proven valuable in demonstrating the extension of inflammatory changes and abscesses in septic sacroiliitis, and in spondyloartropaties may be useful although this is debatable. Scintigraphy gives high sensibility only in early inflammatory changes and low specificity for the diagnosis of sacroiliitis due to high bone turnover in the SIJ, although specific radioprobes are useful in confirming the septic etiology and evaluating additional foci. This complex joint of very limited mobility shows a lot of structural variations and some anatomical degenerative changes due to age, which are necessary to know to an adequate image interpretation and diagnosis of disease.     

Inflammatory spinal disease in psoriatic arthritis: a report from the GRAPPA 2010 annual meeting

Diagnosing axial disease in patients with psoriatic arthritis (PsA) has been largely dependent on identifying inflammatory back pain (IBP), which itself has been difficult to define. We review the criteria used to identify IBP in patients with ankylosing spondylitis (AS) and other forms of spondyloarthritis. Recently, the Ankylosing SpondyloArthritis International Society (ASAS) developed a list of clinical and radiographic criteria for identifying IBP in patients with AS. However, it is more difficult to identify IBP in patients with PsA because generally they have less pain than patients with rheumatoid arthritis or AS. Further, PsA patients may have clinical symptoms of pain but negative radiographs. It may be more useful to identify sacroiliitis or syndesmophytes by magnetic resonance imaging (MRI), since MRI identifies lesions in the sacroiliac joints and the spine much earlier than can be detected on radiographs. In summary, all patients with PsA should be assessed for axial involvement with history, physical examination, and imaging. Patients with psoriasis whose history includes onset of back pain before age 40 years, the presence of night pain, and improvement with exercise but not with rest, or who have limited neck or back mobility, should be referred to a rheumatologist.     

Inflammatory low back pain: high negative predictive value of contrast-enhanced color Doppler ultrasound in the detection of inflamed sacroiliac joints

OBJECTIVE: To determine the value of microbubble contrast agents for color Doppler ultrasound (CDUS) compared with magnetic resonance imaging (MRI) in the detection of active sacroiliitis. METHODS: An observational case-control study of 103 consecutive patients (206 sacroiliac [SI] joints) with inflammatory low back pain according to the Calin criteria and 30 controls (60 SI joints) without low back pain was conducted at the University Hospital of Innsbruck. All patients and controls underwent unenhanced and contrast-enhanced CDUS and MRI of the SI joints. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of unenhanced and contrast-enhanced CDUS were evaluated. RESULTS: Forty-three patients (41%) with 70 of 206 SI joints (34%) and none of the controls nor the 60 control SI joints demonstrated active sacroiliitis on MRI. Unenhanced CDUS showed a sensitivity of 17%, a specificity of 96%, a PPV of 65%, and an NPV of 72%; contrast-enhanced CDUS showed a sensitivity of 94%, a specificity of 86%, a PPV of 78%, and an NPV of 97%. Detection of vascularity in the SI joint was increased by contrast administration (P < 0.0001). Clustered receiver operating curve analysis demonstrated that enhanced CDUS (A(z) = 0.89) was significantly better than unenhanced CDUS (A(z) = 0.61) for the diagnosis of active sacroiliitis verified by MRI (P < 0.0001; 2-sided test). CONCLUSION: Microbubble contrast-enhanced CDUS is a sensitive technique with a high NPV for detection of active sacroiliitis compared with MRI.     

Use of dynamic magnetic resonance imaging with fast imaging in the detection of early and advanced sacroiliitis in spondylarthropathy patients

Objective. To evaluate the new magnetic resonance imaging (MRI) method of dynamic MRI with fast imaging in the diagnosis of sacroiliitis among patients with spondylarthropathy. Methods. Fifteen patients with a history of inflammatory back pain without radiographic evidence of grade II or greater sacroiliitis (group 1), 25 patients with definite ankylosing spondylitis (group 2), and 12 patients with noninflammatory spinal pain (controls) (group 3) were examined. Dynamic MRI with fast imaging was performed after intravenous bolus injection of the contrast agent gadolinium—diethylenetriamine pentaacetic acid. The degree of enhancement was graded as representing acute sacroiliitis, latent sacroiliitis, or no sacroiliitis. Results. Acute sacroiliitis was detected in 22 of 30 sacroiliac (SI) joints in group 1 patients and in 27 of 50 SI joints in group 2 patients; latent sacroiliitis was seen in 25 of 80 SI joints in patients from groups 1 and 2. No group 3 patient was found to have sacroiliitis. Conclusion. Early sacroiliitis can be demonstrated by dynamic MRI in spondylarthropathy patients in whom abnormalities are not revealed by conventional radiography.     

Early detection of sacroiliitis on magnetic resonance imaging and subsequent development of sacroiliitis on plain radiography. A prospective, longitudinal study.

OBJECTIVE: To investigate the diagnostic value of magnetic resonance imaging (MRI) in the detection of early sacroiliitis. METHODS: Twenty-five consecutive HLA-B27 positive patients with inflammatory low back pain and < or = grade 2 unilateral sacroiliitis on conventional radiography (modified New York criteria) were studied. Erythrocyte sedimentation rate, C-reactive protein, plain radiography (PR), and MRI of the sacroiliac (SI) joints were obtained at study entry and PR of the SI joints after 3 years. Each radiograph and MR image set was interpreted independently. SI joints were scored according to the modified New York Criteria for radiological sacroiliitis. MRI scans were also scored for the presence of subchondral marrow edema. The relationship between > or = grade 2 sacroiliitis (by modified New York criteria for radiological sacroiliitis) shown on MRI and the subsequent development of > or = grade 2 sacroiliitis on PR after 3 years was investigated. RESULTS: At study entry > or = grade 2 sacroiliitis was found on MRI in 36 of 50 SI joints. Edema was found in 20 of 50 SI joints. After 3 years > or = grade 2 sacroiliitis was found on PR in 21 of 44 SI joints. The positive predictive value of > or = grade 2 sacroiliitis on MRI for the development of > or = grade 2 sacroiliitis on PR after 3 years was 60%; sensitivity was 85% and specificity 47%. CONCLUSION: Our data suggest that MRI of the SI joints can be used to identify sacroiliitis earlier than PR.     

Diagnosing early ankylosing spondylitis

Diagnosis of ankylosing spondylitis is still delayed by many years. Several efforts have been made in the past few years to shorten this delay. A new set of criteria for inflammatory back pain has performed better than previous sets. MRI has evolved to become the standard imaging modality for the detection of sacroiliitis during early disease, and it clearly outperforms quantitative scintigraphy, which was the standard screening test for many years. Promising new developments such as whole body MRI and ultrasound (sonography) for the detection of enthesitis or sacroiliitis deserve further evaluation. Serum antibodies directed against a 28-kD Drosophila antigen may provide additional diagnostic information. A recently proposed diagnostic algorithm in patients with suspected early ankylosing spondylitis may help physicians confidently diagnose patients before definite radiographic sacroiliitis is detectable. Finally, referral strategies for patients seen by primary care physicians seem to work well and are currently under further valuation.     

Association between inflammatory back pain features,acute and structural sacroiliitis on MRI,and the diagnosis of spondyloarthritis

Clinical Rheumatology - To evaluate the association between inflammatory back pain (IBP) features, acute and structural MRI findings suggestive of sacroiliitis, and diagnosis of spondyloarthritis...     

Atlas of MRI findings of sacroiliitis in pediatric sacroiliac joints to accompany the updated preliminary OMERACT pediatric JAMRIS (Juvenile Idiopathic Arthritis MRI Score) scoring system: Part I: Active lesions

Magnetic resonance imaging (MRI) is an increasingly important tool for identifying involvement of the sacroiliac joints (SIJ) in juvenile idiopathic arthritis (JIA). The key feature for diagnosing active sacroiliitis is bone marrow edema (BME), but other features of active arthritis such as joint space inflammation, inflammation in an erosion cavity, capsulitis and enthesitis can be seen as well. Structural changes may also be seen. Systematic MRI assessment of inflammation and structural damage may aid in monitoring the disease course, choice of therapeutics and evaluating treatment response. In this pictorial essay, we illustrate normal MRI findings and growth-related changes of the SIJ in the pediatric population, as well as the different MRI features of SIJ inflammation. This atlas demonstrates fundamental MRI disease features of active inflammation in a format that can serve as a reference for assessing SIJ arthritis according to the updated preliminary JAMRIS (Juvenile Idiopathic Arthritis MRI Score) scoring system proposed by the MRI in JIA working group of Outcome Measures in Rheumatology and Clinical Trials (OMERACT). The atlas is intended to be read in conjunction with its companion Part 2, Structural Lesions.     

The investigation of sacroiliitis with different imaging techniques in spondyloarthropathies

Purpose The aim of this study was to compare the value of different imaging techniques in spondyloarthropathy (SpA) patients with inflammatory low back pain.Patients and methods We evaluated 54 patients who fulfilled the European spondyloarthropathy classification criteria and had inflammatory low back pain. They were subdivided into two groups according to changes on plain radiography rated on a 0–4 scale according to modified New York criteria. Group A patients had at least grade-2 unilateral or bilateral changes in the sacroiliac (SI) joints, whereas group B included patients with radiologic changes not exceeding grade 0–1. Quantitative SI scintigraphy and magnetic resonance imaging (MRI) were performed to investigate the value of these techniques to the diagnosis of sacroiliitis, and the sacroiliac joint:sacrum uptake ratios were calculated. Scintiscanning was done in 80 healthy subjects to define the normal range.Results The sensitivities of plain radiography, quantitative SI scintigraphy, and MRI were 61%, 55%, and 89%, respectively, among the patients with SpA. MRI and quantitative SI scintigraphy detected sacroiliitis in 97% and 49% of group A, respectively. In group B, these results were 76% and 66%, respectively.Conclusion Magnetic resonance imaging is the most sensitive method for detecting acute or chronic changes in SpA patients with histories of inflammatory low back pain and normal or indeterminate findings on plain radiographs.     

Evaluation of patients with back pain of suspected inflammatory nature

PURPOSE: Detection of early inflammatory back disease is often difficult. Certain clinical characteristics have been reported to increase the likelihood of its detection in referral patients, but the usefulness of these clinical characteristics has not been evaluated in an open population. In our study, we undertook to evaluate the value of the clinical history as a screening test for inflammatory back disease in a general population. PATIENTS AND METHODS: Twenty-three male patients with back pain of moderate duration and with clinical characteristics suggestive of inflammatory back disease were recruited by advertising and were studied by various means, including computed tomography (CT), scintigraphy, and radiography. RESULTS: One patient had radiographic sacroiliitis. Two had positive results for the B27 antigen, and another had positive results for the cross-reacting HLA antigen B7. Eight patients had abnormal scintiscans of the sacroiliac joints. Twenty-one of 23 patients and 20 of 23 control subjects had abnormalities that were detected by CT. Repeat plain radiographs of the pelvis done 36 months after enrollment into the study did not uncover further evidence of sacroiliitis. CONCLUSIONS: These results indicate plain radiographic evidence of sacroiliitis will often not develop in patients with historical features suggestive of inflammatory back disease even with long-term evaluation, thus vitiating the specificity of these historical findings in men with back pain of relatively brief duration.