Why You Might Not Need that Back Pain Test

Medically Reviewed

Guidelines recommend waiting four to six weeks after an initial episode of lower back pain before having X-rays or other back pain tests done. That’s because these scans often reveal abnormalities that can lead to unnecessary treatment, which is both costly and potentially harmful.

For older adults, there is a greater chance that lower back pain is related to a serious condition. Consequently, some guidelines remove the restriction on early imaging for older patients. But little research exists documenting the potential benefits or harm of using early imaging when diagnosing lower back pain in older adults.

A 2015 study published in JAMA reviewed data for more than 5,200 patients 65 and older who were treated for lower back pain after reporting an initial episode. At the end of one year, the data showed no significant differences in outcomes for patients who received early scans and those who did not.

Early imaging or the lack of it had no impact on the discovery of serious illnesses such as cancer. Nor did it lead to more or fewer adverse effects from treatment. What it did was result in greater expense from more but unnecessary use of medical resources.

If you are over 50 and your doctor suggests the need for an X-ray or other scan for your back, be sure to discuss the pros and cons first. Ask what will happen after the scan, and what might happen if you wait before having it done.

Following are some of the tests used in diagnosing back pain that your doctor may use.

Lab tests

Routine blood tests help determine the cause of back problems in a few situations. Results may reflect the presence of inflammation and/ or an infection.

For example:

• Blood levels of alkaline phosphatase, an enzyme released by bone-forming cells (osteoblasts), are often extremely high in people with active Paget’s disease (a condition characterized by excessive overgrowth of bone). This can cause vertebral compression fractures and spinal stenosis.

• Blood calcium levels are elevated in people with hyperparathyroidism. This condition, along with osteoporosis, can lead to vertebral compression fractures.

• Prostate-specific antigen (PSA), which is elevated in men with prostate cancer, can be measured by a blood test to determine whether back pain may be due to the spread of prostate cancer.

• Abnormal proteins in blood and urine are often present in people with multiple myeloma (cancer of the plasma cells, a type of white blood cell).

Imaging Studies

Diagnostic imaging studies provide a view of the bones and soft tissues that constitute muscles, ligaments, cartilage, tendons and blood vessels. These studies are typically recommended only when pain worsens despite initial care, or when the doctor suspects nerve damage or a serious condition may be responsible for the back pain.

Experts advise against routine imaging studies when no particular cause of the pain is identified through the physical exam, patient history and laboratory tests. When imaging is ordered, the study chosen depends in large part on what is suspected to be causing the pain.

X-rays For chronic pain and new-onset back pain lasting longer than four to six weeks, X-rays should be the first imaging study. They are especially useful for detecting fractures, tumors and infection. Although X-rays tend to be overused, they are useful for people over age 50, because this age group has a greater risk of malignancy and vertebral fractures. Modern X-rays are low in radiation but should be used only when necessary. X-rays are widely available and relatively low cost.

Computed tomography (CT) scans During a CT scan, also called a computerized axial tomography (CAT) scan, a thin X-ray beam is rotated around a specific area of the body to create a cross-sectional picture. CT scans are 10 to 20 times more sensitive than X-rays; they provide better soft-tissue detail and good detail of the vertebrae. Although CT myelograms or magnetic resonance imaging (MRI) scans are even more useful for examining the soft tissues (for example, herniated disks), CT scans are still best for studying bone problems, such as fractures. CT scans are considerably more expensive and deliver more radiation than conventional X-rays.

CT myelogram This procedure combines a CT scan and a myelogram (also known as myelography), a diagnostic tool in which contrast dye is injected into the fluid of the spinal canal. The contrast dye illuminates the spinal canal, cord and nerve roots during imaging. A CT scan is taken after the dye is injected; the images produced clearly show both the bony structures of the spine and the nerve structures.

The injection carries the risk of infection and side effects such as nausea, headaches and pain or discomfort at the site of injection. People are required to sit or lie with their head elevated for six to eight hours afterward. These scans offer the best detail of bone and soft tissue. CT myelograms are usually performed only prior to surgery or after failed surgery.

MRI During an MRI the body is surrounded by a powerful magnet. The magnet causes water molecules within the body to vibrate and give out characteristic signals, which are converted into two-and three-dimensional images. No X-rays are involved. This test provides the clearest images of soft tissues and does not involve the use of radiation.

Despite its ability to generate clear, precise images of soft tissue, MRI may not generate a useful image of the bones in the spine. Consequently, it is not recommended for early diagnosis of back pain unless the doctor suspects disk, nerve or soft tissue involvement.

Even when an MRI is warranted, some drawbacks must be considered. First, the abnormalities revealed may not necessarily be the cause of the back pain. An MRI cannot identify back strains and spasm, for example. Second, because people must lie perfectly still for a long period (anywhere from 30 minutes to two hours) in a relatively small space, the procedure may be uncomfortable and difficult to tolerate, especially for people who are claustrophobic. (An open MRI produces less claustrophobia than a closed machine but generally does not provide high-quality images and is not recommended if you can tolerate a standard MRI scanner.) Third, MRI cannot be used in people with devices such as implantable cardioverter-defibrillators, pacemakers or aneurysm clips. If you have any of these devices or have questions about the safety of an MRI scan, speak with your doctor.

Bone scans Bone scans measure the amount of radioactivity emitted from bone after an injection of a bone-seeking compound that contains technetium, a radioactive metal. The bone is scanned two to three hours after the injection, and information regarding distribution of the radioactive compound in the bone is fed into a computer, which produces a one- or two-dimensional image of the bone.

An area of bone that shows an increased uptake of technetium has a higher rate of bone turnover, which can be the result of a fracture or nonunion that was not identified on an X-ray. This finding can also indicate the presence of metastatic cancer, Paget’s disease or osteomyelitis (a bacterial infection of the spine).

The amount of radiation delivered is similar to that of a CT scan. This technique can be used to identify fractures in both the central and peripheral areas of the body.

Electrical Tests

Three basic types of electrical tests may be used in difficult cases involving leg pain that has persisted for over a month. These tests may help the doctor pinpoint the source of pain or numbness or suggest the cause of pain (for example, whether it is due to disk herniation or nerve damage from an unrelated disorder, such as diabetes).

Electromyography: In this test, electrodes are used to measure muscle abnormalities.

Nerve conduction and sensory-evoked potentials Both of these tests examine nerve function by measuring how fast the nerves conduct impulses.

These tests are used only when the diagnosis is in doubt. However, there is still some debate over their usefulness.