A Look At Two Recent Studies
Spondyloarthritis (SpA) remains grossly under diagnosed, with an average delay of eight to 11 years between symptom onset and diagnosis. This is important to rectify, as SpA patients with delayed diagnosis consistently show worse outcomes in “disease activity, function, spinal mobility and/or radiographic damage,” (1) as well as a less favorable treatment response. Incidentally, one multivariate analysis indicated that “a prior diagnosis of mechanical back pain was an independent factor associated with diagnostic delay.” (1)
We look at two recent studies, one – exploring undetected AS, and the other – the potential pitfalls in relying too heavily on symptoms and clinical features to predict sacroiliitis in kids.
The first study (2) looked at first-degree relatives of HLA-B27+ ankylosing spondylitis patients to examine the prevalence of undetected SpA in that population.
Fifty-one first-degree relatives (FDRs) of patients with ankylosing spondylitis were included in an ongoing, prospective study. “Back pain was reported by 59% FDRs, 18% of whom had inflammatory back pain… Low-grade sacroiliitis was observed on X-ray in 6% of FDRs, and cervical syndesmophytes were observed on X-ray in one person.”
Of the 51 FDRs, who were not diagnosed with any form of SpA at the time of the study, 13 did indeed fulfill criteria for an AS diagnosis.
Interestingly, while more frequent inflammatory back pain and higher overall disease activity were seen in FDRs who met AS criteria, no differences were seen in inflammatory markers, peripheral and extra-articular disease, or HLA-B27 status. Also, “six of the FDRs who did not meet any [AS] criteria had abnormalities observed on imaging that may be consistent with SpA, according to the researchers.”
The second study (3) looked at children who were newly diagnosed with juvenile spondyloarthritis to evaluate the “prevalence of sacroiliitis at diagnosis of juvenile spondyloarthritis (JSpA) and the accuracy of physical examination and back pain to detect sacroiliitis.”
This was a cross-sectional study of 40 children who were newly diagnosed with JSpA, and 14 healthy controls.
The study findings suggest that back pain and clinical exam findings are insufficient at accurately predicting sacroiliitis in kids.
“Of the subjects with active sacroiliitis only three (38%) reported a history of back pain or tenderness on palpation of the sacroiliac joints. The positive and negative predictive values of clinical exam features and back pain for detection of sacroiliitis were low.”
The researchers added, “Active sacroiliitis by MRI is common at diagnosis in JSpA and is frequently asymptomatic. Children who are HLA-B27+ and have elevated CRP levels have the highest probability of sacroiliitis.”
Studies such as these are important as they shed light on various aspects of diagnostic modalities and theories, and help highlight gaps in the current approach to diagnosing spondyloarthritis.
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