High Pain Sensitivity in Patients Linked to Worse Clinical Outcomes

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by Joana Carvalho |

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People with axial spondyloarthritis (axSpA) who had higher pain sensitivity were more likely to have worse clinical outcomes, according to a study that found chronic pain to be common in these patients.

The study, “Chronic pain and assessment of pain sensitivity in patients with axial spondyloarthritis: Results from the SPARTAKUS cohort,” was published in The Journal of Rheumatology and led by scientists in Sweden.

axSpA is a type of arthritis that mainly affects the joints of the spine. It is known as ankylosing spondylitis (AS) when joint damage is visible on regular spine X-rays and as non-radiographic axial spondyloarthritis (nr-axSpA) when no damage can be seen.

As in other rheumatic disorders, pain is a common complaint among patients with axSpA. Pain can manifest itself during fluctuating or more persistent episodes, and become chronic over time.

A previous study carried out by the same group of investigators found that nearly half (nearly 45%) of AS patients experience chronic widespread pain.

“Owing to the need for better understanding of pain in axSpA and considering the high [chronic widespread pain] prevalence previously observed,” the researchers wrote, “a more comprehensive assessment of different pain aspects, including pain sensitivity, in a well-defined axSpA cohort [group] would be of value.”

Here, the scientists conducted a population-based study that compares pain distribution, intensity, and sensitivity in patients with AS or nr-axSpA.

The study, called SPARTAKUS, enrolled 175 patients with axSpA, including 120 with AS and 55 with nr-axSpA, who were followed at the Skåne University Hospital in Sweden, from 2015 to 2017.

The investigators gathered clinical data from medical records, as well as information on pain intensity, duration, and distribution through questionnaires. Pain sensitivity was measured by computerized cuff pressure algometry, a method in which a cuff was placed around the lower leg to be gradually inflated until the patient started experiencing pain.

Statistical analyses were then used to compare pain measures in both groups of patients, and to identify possible relationships between pain sensitivity and other clinical outcomes.

Participants in SPARTAKUS had been experiencing disease symptoms for a mean of 27 years. Nearly half (46%) were women.

In the overall group of patients, 44% reported to have experienced chronic widespread pain, and 33% said they had experienced chronic regional pain, affecting a mean of 4.8 body regions.

Nearly half (42%) of the patients also said their pain was unacceptable, corresponding to a value greater than 40 mm in a 0–100 mm visual analog scale, where 0 indicated no pain and 100 suggested worst imaginable pain.

No significant differences were found between the two patient groups in any of the pain measures analyzed, “suggesting that the disease subgroups have a similar pain presentation,” the investigators wrote.

Yet, statistical analyses found that patients who had a lower pain tolerance (higher pain sensitivity), were more likely to have poorer clinical outcomes, including unacceptable pain, a greater number of painful body regions, longer symptom duration, worse fatigue and anxiety, higher disease activity, and lower health-related quality of life.

“The results indicate that patients with AS and nr-axSpA, in line with most clinical characteristics, have a similar pain burden and they highlight large unmet needs regarding individualized pain management, regardless of axSpA subgroup,” the investigators concluded.