A 28-year-old man with no significant medical history presents to his primary care physician complaining of intermittent low back pain for the past 4 months. He says the low back pain is worse in the morning along with stiffness lasting approximately one hour which improves as the day goes on. On physical examination, performing a forward bending test shows no unevenness in the spine and ribs, but spinal flexion is moderately limited. Straight leg raise test is negative bilaterally. Sensation is intact in the bilateral legs with no numbness or tingling. The patient denies recent fever, weight loss, waking up at night due to pain, urinary retention, or bowel incontinence. He also denies any other symptoms currently. Initial x-rays of the lower spine and pelvis show no evidence of obvious spinal changes or sacroiliitis.
Which of the following is the most appropriate next step in management of this patient?
B) Order erythrocyte sedimentation rate and C-reactive protein
This patient’s presentation of morning stiffness, low back pain, limited spinal flexion in a young man is concerning for ankylosing spondylitis. Diagnosis requires obtaining a thorough history, including asking for red flags that would raise concern for malignancy, infection, or spinal compression such as weight loss, nocturnal awakening, fever, and change in urinary or bowel patterns. Performing a complete physical exam helps to differentiate between neurological, musculoskeletal, or rheumatological processes. According to the 2013 Assessment of Spondyloarthritis International Society (ASAS) modified Berlin algorithm– the first step of diagnosing ankylosing spondylitis is to obtain X-rays. If X-rays are negative, consider the presence of other clinical evidences such as enthesitis, dactylitis, uveitis, family history, inflammatory bowel disease, psoriasis, asymmetrical arthritis, positive response to nonsteroidal anti-inflammatory drugs, and raised ESR/CRP on labs. Having ≥4 features suggests the diagnosis of ankylosing spondylitis. If less than 4 features are present, the next step is to obtain HLA-B27, which carries a >90% sensitivity for ankylosing spondylitis. If HLA-B27 tests negative, then other diagnoses should be considered.
Answer Choice A: Anti-histone antibody, is incorrect. Antihistone antibody is associated with drug-induced lupus and systemic lupus erythematosus (SLE). Some medications that induce lupus include procainamide, hydralazine, quinidine, and isoniazid.
Answer Choice C: Order MRI of the spine, is incorrect. MRI should be considered after obtaining HLA-B27; it is not indicated at this time. Per the Berlin algorithm – if a patient has only 0-1 spondyloarthritis features and test positive for HLA-B27, then obtain MRI.
Answer Choice D: Order rheumatoid factor/anti-CCP antibodies, is incorrect. Rheumatoid factor and Anti-CCP antibodies are associated with rheumatoid arthritis.
Answer Choice E: Refer to physical therapy, is incorrect. More investigation is warranted at this time before referring to physical therapy.
Key Learning Point
A negative x-ray does not necessarily rule out ankylosing spondylitis. Follow the described steps above for diagnosis (reference: 2013 Assessment of Spondyloarthritis International Society (ASAS) modified Berlin algorithm). Remember sensitivity can be remembered as “SNOUT” – a highly sensitive test rules out a disease when they are negative, meaning if HLA-B27 is negative, then the patient likely does not have ankylosing spondylitis; however, remember this is not 100% confirmatory.
