PHILADELPHIA — A set of either five or six criteria helped physicians identify patients with back pain who had a high likelihood of having spondyloarthritis in a German study.
The number of helpful criteria varied depending on whether patients underwent testing for HLA-B27, Annalina Braun said at the annual meeting of the American College of Rheumatology. When the assessment included testing for HLA-B27 positivity, a total of six assessment criteria proved helpful: back pain that improves with movement but doesn't improve with rest, pain that improves within 48 hours on treatment with an NSAID, age of pain onset of 35 or less, alternating buttock pain, a history of enthesitis, and a positive HLA-B27 test.
Patients who met at least three of these six criteria had spondyloarthritis (SpA) with a sensitivity of 79% and a specificity of 60%, and 76% of all SpA cases in the validation cohort of the study had correct classification, said Ms. Braun, a researcher at the Rheumazentrum Ruhrgebiet in Herne, Germany.
The study run by Ms. Braun and her associates included 950 patients with back pain seen during April 2007–June 2009.
When HLA-B27 status wasn't included as part of the primary care assessment, a set of five criteria had the best performance for case identification. Four of those were identical to those in the prior set: back pain that improves with movement but not rest, pain that improves within 48 hours on NSAID treatment, age of onset of 35 or less, and alternating buttock pain. Awakening during the second half of the night because of back pain rounded out this list. In Ms. Braun's study, the presence of at least four of these five criteria identified SpA patients with a sensitivity of 48% and a specificity of 86%, and accounted for 71% of SpA cases in the validation cohort studied.
A group of 36 rheumatologists then performed a follow-up assessment on 322 of these patients a median of 20 days following their initial examination. The average age of the 322 patients was 36, with a range of 17–55. The median duration of back pain was 2.5 years.
The rheumatologists diagnosed axial SpA in 113 of the 322 patients (35%). Ms. Braun and her associates then analyzed which diagnostic criteria initially assessed by the orthopedic surgeons correlated best with the SpA diagnoses rendered by the rheumatologists. These case-ascertainment criteria now need validation in additional patient populations, Ms. Braun said.
The study was supported by an unrestricted grant from Abbott Germany. One of the coauthors is an employee of Abbott Germany; Ms. Braun and the other coauthors had no disclosures.
The presence of four criteria identified SpA patients with a sensitivity of 48% and a specificity of 86%.
Source MS. BRAUN