Patient History

The patient history is an important feature in the diagnosis of SpA. Classic historical features involve inflammatory back pain, enthesitis, peripheral arthritis, and dactylitis. The cornerstone for diagnosis of axial SpA is dependent on the patient reporting the presence of inflammatory back pain lasting longer than 3 months, which began in an individual before the age of 45 years old. Inflammatory back pain is defined as having an insidious onset, improving with exercise and not with rest, and oftentimes pain at night that improves upon getting up and moving. Peripheral SpA is based upon a history of oligoarticular arthritis, enthesitis, or dactylitis. There are other historical non-musculoskeletal features that are important to elucidate and include inflammatory eye symptoms (photophobia, blurred vision), inflammatory bowel symptoms (diarrhea, hematochezia), recent GI or GU infection, and psoriasis. As one hallmark of SpA is a favorable response to NSAIDs, it is useful to assess if the patient has tried these drugs and their effect on the presenting symptoms. Finally, family history of SpA, psoriasis, uveitis/iritis, or IBD should be assessed.

Physical Exam

On physical exam, it is important to evaluate for axial, peripheral, and non-musculoskeletal findings. Axial symptoms can be investigated by looking for low back pain associated with sacroiliac joint tenderness and decreased range of motion. There are multiple objective measurements that can be performed to monitor disease progression over time. These include the Schober’s test (measuring lumbar flexion distance at the level of L5), occiput-to-wall (measuring cervical neck extension), lateral spine side flexion, thoracic chest expansion, and hip internal rotation. Enthesitis is a hallmark of SpA, and there are multiple sites of ligament and tendon insertions that can be evaluated, but most commonly the Achilles tendon insertion of at the heel is assessed. There are multiple validated enthesitis indices from the Berlin Enthesitis Index (BEI), Masstricht AS Enthesitis Score (MASES), and Spondyloarthritis Research Consortium of Canada (SPARCC) that can be performed [12]. A full peripheral joint exam should be performed to assess for tenderness, effusions, warmth, and limitation of range of motion as well as evidence of dactylitis in the fingers or toes.

A full physical exam should additionally be conducted to evaluate for extra-articular manifestations. This should include a thorough skin evaluation to look for signs of psoriasis along extensor surfaces, behind ears, in the umbilicus, and within the crease of the buttocks; evaluation for signs of gastrointestinal or sexually transmitted diseases; and evaluation for SpA comorbidities such as cardiovascular and respiratory disease.

Lab Testing

There are no diagnostic labs for SpA. Common lab tests include HLA-B27 and acute phase reactants such as ESR or CRP, which may serve to support clinical suspicion. It is important to note that the absence of these does not rule out SpA. Additional tests may be ordered related to details of the history and physical exam, such as fecal calprotectin or sexually transmitted infection testing if considering IBD-associated SpA or reactive arthritis, respectively. All patients need to be assessed for blood cell counts, liver and kidney function, hepatitis and HIV screening, and TB screening depending upon their treatment plan.

Imaging

X-rays are the first-line imaging modality, which can demonstrate SI joint abnormalities ranging from blurring of the joint margins to evidence of sclerosis and erosions and ultimately with complete joint fusion. These images can also be obtained using the Ferguson view, entailing a 20-degree caudocephalic AP X-ray. The findings are usually bilateral in SpA, and unilateral findings should prompt one to consider alternative diagnoses. Spinal X-rays in AS can demonstrate vertebral body squaring, shiny corner sign (small erosions at the corners of the vertebral bodies), ossification of spinal ligaments/discs, enthesophytes, and progressive bamboo spine. Peripheral joint X-rays are more variable and may not always demonstrate abnormality. However, in PsA, X-rays in established disease often demonstrate erosive disease, particularly in the hands and feet in which the classic pencil-in-cup appearance of IP joints can be observed.

MRI can also be performed in the appropriate clinical setting, such as a high suspicion for axial SpA in the setting of normal X-rays but a suspicious clinical history. The most appropriate MRI sequences to identify SI joint inflammation are T1 and STIR. MRI findings will demonstrate synovial enhancement and increased STIR signal representing edema during acute inflammation and increased T1 signal representing bone marrow metaplasia suggesting past inflammation.

Imaging can also be useful for monitoring progression over time or to determine changes in therapy. For example, a patient with AS may complain of continued back pain while on therapy, and X-rays have not changed in the past several years. In this case an MRI can help determine if features of joint inflammation are present to warrant therapy changes.

Differential Diagnosis

Based upon the appropriate workup, an appropriate differential diagnosis must be considered that includes both inflammatory and noninflammatory disorders. Other disease processes to consider include the following: mechanical back pain, osteoarthritis, fibromyalgia, diffuse idiopathic skeletal hyperostosis (DISH), iliac condensans ilii, Paget’s disease, Brucellosis, Whipple’s disease, SI joint infection, gout, and osteochondrosis.

Treatment

The 2016 SPARTAN/GRAPPA recommendations for the management of axial SpA support use of physical therapy for all patients. NSAIDs are recommended as first-line therapy, followed by TNF-inhibitors and then alternate biologic agents [13]. Specific agents and uses are discussed below.

Disease Monitoring

Comorbidities

There are a number of relevant comorbidities in patients that have SpA, including cardiovascular disease (CVD), obesity, diabetes, inflammatory bowel disease, ophthalmic disease, malignancy (lymphoma), restrictive lung disease, liver/kidney disease, and depression/anxiety. Cardiovascular disease has an incidence between 3.3% and 9.6% in patients with PsA [24], and a hazard ratio of 1.41 relative to matched controls in AS [25]. The rheumatologist should help manage cardiovascular risk in conjunction with the Primary Care Physician. EULAR recommendations for CVD management include optimally controlling rheumatologic risk and using NSAIDs with caution. Basic screening should be performed with regard to monitoring blood pressure, monitoring lipids, and counseling on smoking cessation. Other relevant screening should be performed such as monitoring for obesity with appropriate counseling, monitoring fasting blood glucose or hemoglobin A1C, monitoring liver and kidney labs, and monitoring for symptoms regarding eye or GI involvement of disease.

Prognosis

Overall outcomes are generally good for SpA if diagnosed and treated in an appropriate amount of time; however, up to 30% of patients with SpA will be on disability 20 years after diagnosis [26]. Earlier diagnoses usually manifest as undifferentiated SpA, which carries a 40% progression rate to diagnosed AS [27]. Patients with SpA are at high risk of bone fracture, and require close monitoring for bone health, as well as an ongoing need for physical and occupational therapy. Trauma is also a concern in these patients, as the higher rate of spinal fracture can lead to neurologic emergencies such as spinal cord impingement or cauda equina syndrome.

Questions