Biomarkers for chronic pain

Chronic pain is an important quality of life issue for millions. The current epidemic of opiate use underscores the struggle to cope with chronic pain. Diagnosing chronic pain is usually done by self-report. Obviously, people know when they are in pain. Discovering the root cause of pain is not trivial. Diagnosis may require a great many tests and every delay is misery for the patient. Blood tests exist but (from what I can tell) track complications from treatment and do not greatly help diagnosis. One pain management organization uses the following panel of blood tests for new patients:

AM Cortisol
AM Pregnenolone
Erythrocyte Sedimentation Rate (ESR)
C-Reactive Protein
Total Testosterone

In reading the rationale for these tests, it is not clear how all of these are related to the physiology of pain. It’s not clear if there is any blood work that can be done to help assess the source of chronic pain.

Cortisol and blood pressure may be elevated if the patient is already experiencing extreme pain. Ideally, these conditions would be reduced in the case of successful treatment. How does pain change cortisol or blood pressure? Maybe through the psychological stress that pain causes. Maybe something else.

Pregnenolone and cortisol are adrenal hormones. They can correlate with pain, but possibly be increased or reduced as a result of pain induced stress. Likewise, C-reactive protein may report inflammation, and inflammation may be the cause of pain. On the other hand, pain itself may cause C-reactive protein or erythrocyte sedimentation rate to be elevated through mechanisms that are largely unknown.

A testosterone test is administered in order to screen for an underlying hormonal problem, determine whether the patient is already on a dose of opiates that is suppressing testosterone production, and to establish a baseline so that this complication can be detected and avoided later on in the course of treatment.

My point is that none of these tests will tell a physician that pain is definitely neurological/inflammatory/CNS-related. They won’t tell the physician with any certainty if the patient is an addict who needs a fix. At best, these tests might rule out inflammatory problems as the root cause of pain.

What are the biomarkers of specific pain causes? More tomorrow.