Published: Dec 12, 2014

By Pam Harrison , Contributing Writer, MedPage Today

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Patients with psoriasis have a higher prevalence of lower axial back pain than the general population while inflammatory back pain (IBP), spondyloarthritis (SpA), and alternating buttock pain are also more likely to occur in those with psoriasis than those without, National Health and Nutrition Examination Survey (NHANES) data indicates.

A total of 153 subjects between 20 and 69 years of age in the 2009-2010 NHANES survey reported having been diagnosed with psoriasis or psoriatic arthritis (PsA). Among those with psoriasis/PsA, the prevalence of axial pain lasting for 6 or more weeks was 39.6% (95% CI 25.5-53.6) compared with 27.2% (95% CI 24.7-29.8) for those with no psoriasis (P=0.07).

For pain lasting for 3 months or more, the prevalence of axial pain was 31.1% (95% CI 17.2-20) in the psoriasis/PsA group compared with 18.9% (16.8-21.1) for the general population (P=0.04).

In contrast, the difference in axial pain between those with and without psoriasis using a 6-week duration criterion was not significant at 39.6% versus 27.2% (P=0.07), respectively.

Inflammatory back pain defined by Berlin criteria 7b and 8a was also significantly more prevalent in those with psoriasis/PsA at 15.3% (6.5-24.2) compared with 5.7% (4.7-6.8) in the general NHANES population (P=0.04) according to Berlin 7b criteria, and 17% (7.8-26.3) versus 5.4% (4.7-6.1) according to Berlin 8a criteria, respectively (P=0.02).

The prevalence of SpA using the Amor classification criteria for SpA was again significantly higher in the psoriasis/PsA group at 8.6% (4.3-13) compared with 0.6% (0.3-0.9) for the non-psoriasis/PsA group (P=0.001).

This held true when investigators used ESSG SpA classification criteria for SpA, as the authors point out.

When the two criteria were combined, 14.3% (8.6-20) of the psoriasis/PsA group met the criteria for SpA using either Amor or ESSG criteria compared with only 1.5% (1.1-1.9) for those without psoriasis/PsA (P<0.001).

Finally, alternating buttock pain lasting over 3 months was reported by 7.2% (3.1-11.3) of the psoriasis/PsA group versus 2.4% (1.8-3.0) for those without psoriasis/PsA (P=0.03).

“The primary study objective was to provide U.S. population-based prevalence estimates for axial spinal symptomatology, IBP, SpA, and selected co-morbidities among self-reported, medically diagnosed psoriasis,” Nicole Thom, MD at Cedars-Sinai Medical Center in Los Angeles, and colleagues wrote online in Arthritis Care and Research.

“And as research continues to support multiple comorbidities in psoriasis — including IBP — it raises the question if primary care physicians, rheumatologists, and dermatologists should be screening for these co-morbidities.”

The NHANES 2009-2010 survey included a questionnaire for IBP and SpA that was created to provide population-based prevalence estimates for four published IBP classification criteria.

Overall, almost one-third of 4,950 adults included in the NHANES survey reported a history of chronic axial pain.

Almost 90% of both the psoriasis/PsA group and the non-psoriasis group reported having current axial pain at a mean duration of pain for both groups of 13.2 years.

On the other hand, constant pain was more frequent at 27.8% in the psoriasis/PsA group compared with the non-psoriasis/PsA group at 16.6% (P=0.01) as was pain recurring in cycles lasting over a month at 9.6% versus 5.2% for the psoriasis group versus the non-psoriasis group, respectively (P=0.05).

“The rapid development of axial pain within one hour to a day was significantly higher in the psoriasis group as well (23.3% versus 13%; P=0.01),” investigators add.

“And these findings may change the way the psoriasis patient is approached in primary care clinics when they present with sudden-onset back pain and buttock pain.”

A limitation of the study was the lack of formal validation of self-reported medical provider diagnosis of psoriasis.

Investigators point out that back pain, while a common complaint in primary care clinics, usually arises from mechanical and not inflammatory etiologies.

The fact that they found a higher prevalence of alternating buttock pain in patients with psoriasis/PsA coupled with the observation that the majority of subjects with psoriasis and back pain were under the age of 45 “support back pain of possibly inflammatory etiology in these subjects.”