It is currently believed that there are 3 main problems with the 1984 diagnostic criteria.
(1) The requirement for x-ray changes in the criteria makes it impossible to obtain a diagnosis in early stage patients (with mid-axis joint symptoms but without sacroiliac joint x-ray changes).
(2) It is difficult to distinguish accurately between grade I and II sacroiliac joint X-ray changes in clinical practice. According to the diagnostic criteria, the differentiation of grade I and II radiographic changes is an important issue of “all” or “none”. This criterion is more difficult to operate in practice, and about 20% of patients may be incorrectly graded.
(3) The determination of thoracic and spinal mobility is not sensitive to early stage patients (patients with limited thoracic and spinal mobility are mostly advanced).
In addition, the criteria do not focus on HLA-B27 and revisit the role of acute iritis in the diagnosis, and do not differentiate well between undifferentiated spondyloarthropathies.
Challenges in the early diagnosis of SpA
In recent years, research on SpA has challenged its original diagnostic criteria.
The duration of disease determines the presence or absence of radiographic changes in patients with SpA Clinical studies have shown that it takes at least 5 to 10 years from the onset of IBP symptoms to the appearance of radiographic changes, and the positive rate is positively correlated with the duration of disease. Therefore, time or disease duration is a key factor in the presence or absence of X-ray changes in patients with SpA.
The means of examination affects whether inflammatory changes in SpA can be detected Studies have shown that magnetic resonance imaging (MRI) examination can detect inflammatory manifestations (subchondral bone marrow edema) in patients without obvious X-ray sacroiliac joint changes; if MRI shows sacroiliac joint ≥ grade II, its positive predictive value for plain X-ray plain radiographs showing sacroiliac joint ≥ grade II after 3 years is 60%, with sensitivity and specificity of 85% and 47%, respectively. Therefore, the means of examination is another key factor in exploring inflammation of the sacroiliac joint.
Clinical significance of sacroiliac joint changes Although sacroiliac joint changes are significant in the diagnosis of the disease, studies have shown that there is no significant correlation between a patient’s life, disease activity, level of pain at night, need for treatment, and response to treatment and the presence or absence of x-ray sacroiliac joint changes.
As awareness of the early stages of the disease increased, the European Spondyloarthropathy Study Group (ESSG) and Amor introduced their respective diagnostic criteria in the 1990s.
However, none of these criteria are applicable to the early diagnosis of SpA due to the following reasons.
(1) They are not applicable to patients without X-ray sacroiliac joint changes;
(2) The diagnostic sensitivity and specificity of ESSG criteria for SpA are 86% and 87%, respectively, but the diagnostic sensitivity for early cases is only 66%;
(3) The application of MRI was not included;
(4) Lack of clinical features to distinguish mesial and peripheral AS.
Currently, it is believed that the accompanying X-ray sacroiliac joint changes are the result of chronic, long-term inflammatory changes of the disease and are a sign of disease severity, rather than progressive inflammatory changes, and thus should not be a necessary condition for disease diagnosis. Therefore, patients with mid-axis joint symptoms should be considered to have the same type of disease as AS, regardless of the presence or absence of radiographic sacroiliac joint changes. This concept is similar to that of early rheumatoid arthritis (RA) (where imaging changes are an indicator of RA severity rather than a diagnostic necessity), and it also alleviates the difficulty and pressure on clinicians to differentiate between grades of radiographic sacroiliac joint changes.
Subclinical profile of SpA
According to the 1984 criteria, there are four clinical situations in which a patient with IBP can be diagnosed with AS based on the timing of the radiographic sacroiliac joint changes at the time of the first visit. In other words, the diagnosis was confirmed at the first visit, accounting for 10%-30%; the diagnosis was confirmed after 5 years of follow-up with X-ray sacroiliac joint changes, accounting for 50%-70%; the diagnosis was confirmed after 10 years of follow-up with X-ray sacroiliac joint changes, accounting for 15%-25%; and the diagnosis was confirmed after 15 years of follow-up without X-ray sacroiliac joint changes, accounting for 10%-15%.
In addition, the following should be noted: First, chronic back pain is a common symptom in the general population, and its causes are diverse. Studies have shown that chronic back pain associated with SpA accounts for only 5% of the total chronic back pain population, regardless of the presence or absence of x-ray sacroiliac joint changes.
Second, although typical IBP is important for the diagnosis of AS and is the main reference point and starting point for most diagnostic criteria, IBP is present in only 70% to 80% of patients with AS. In addition, IBP is seen in 20% to 25% of patients with mechanical low back pain (spine-related pain).
Finally, there are no widely accepted early diagnostic criteria for SpA without radiographic sacroiliac joint changes.
Based on the above analysis, IBP alone is not sufficient to diagnose SpA, and it is necessary to establish a new set of diagnostic criteria aimed at including both early and non-IBP SpA patients.
Ideally, the early SpA classification criteria should contain at least 3-4 data to achieve better specificity, meet the diagnostic needs, include all relevant data (including MRI), reflect the whole picture of the disease (pre-radiological changes, radiological changes) and different weights of relevant data.
New criteria for early diagnosis
In 2009, the International Spondyloarthritis Assessment Task Force (ASAS) proposed a multifaceted approach to diagnosis (see our November 19, 2009, A8 and A9 pages for details), dividing patients into multiple entry pathways: those with imaging abnormalities, plus one or more SpA features; those with three or more SpA features; those with IBP, plus two or more SpA features; or those with HLA- B27 positive, plus 2 or more SpA features. Among the imaging abnormalities, in addition to the original bilateral sacroiliac joint grade II or unilateral grade III or higher X-ray abnormalities, MRI sacroiliac joint inflammatory changes were added, which increased the diagnostic sensitivity from 66% to 83%.
This criterion inherits the traditional concept of SpA with IBP and sacroiliac joint imaging changes, and also emphasizes the special population with HLA-B27(+) and early SpA with SpA features only, thus conforming to a more extensive, complex and diverse clinical use.
The above criteria give importance to patients with acute anterior uveitis and/or HLA-B27(+). Although acute anterior uveitis has many etiologies, half of them are associated with rheumatic diseases; a significant number of patients with acute anterior uveitis associated with HAL-B27 are in turn associated with SpA; therefore, in clinical practice, if the above multiple diagnostic pathways and conditions can be considered together and used separately or in combination for different patients according to their specific conditions, it will likely significantly improve the SpA with different clinical manifestations The diagnosis rate.