This patient with nonspecific low back pain does not require additional testing. In patients presenting with low back pain, the history and physical examination should focus on determining the likelihood of a specific underlying condition causing the back pain and identifying any neurologic involvement that may be present. In patients in whom low back pain cannot be attributed to a specific disease or spinal abnormality (defined as nonspecific low back pain), the American College of Physicians and other organizations recommend against imaging or obtaining other diagnostic studies routinely. Such testing should be reserved for patients in whom a serious underlying condition is suspected, those with severe or progressive neurologic deficits, or patients who do not have symptom improvement after 4 to 6 weeks of conservative management. As this patient's pain meets the definition of nonspecific low back pain, no additional imaging or testing is indicated before initiating therapy.

An erythrocyte sedimentation rate is a marker of inflammation and is indicated only if a systemic inflammatory process or infectious cause of low back pain is suspected, neither of which is suggested in this patient.

Ankylosing spondylitis is a spondyloarthritis with systemic features that typically presents with low back pain, morning stiffness, and sacroiliitis; extra-articular manifestations may include uveitis. HLA-B27 testing can be useful in the appropriate clinical scenario to support the diagnosis of ankylosing spondylitis; however, HLA-B27 can be positive in other disease processes as well. This patient has no additional symptoms associated with his back pain and no suggestive findings on examination, making the diagnosis of ankylosing spondylitis unlikely.

Radiography of the lumbar spine is indicated only if fracture, degenerative arthritis, or an inflammatory process such as ankylosing spondylitis is suspected, none of which are likely diagnostic considerations in this patient.