The aim of the search was to retrieve studies evaluating the prognostic value of laboratory tests and/or imaging tests in terms of radiological and functional outcome and clinical remission. Details of the selected studies are reported as online supplementary material S4.
We found 35 studies for laboratory tests and 12 studies for imaging tests.
Laboratory tests
Included studies evaluated mainly RF (19 studies24 ,25 ,47 ,53–68) and ACPAs, in particular anti-CCP antibodies (25 studies24 ,25 ,47 ,55–66 ,69–78) (see online supplementary materials S6). Apart from three studies47 ,61 ,64 on clinical remission, all included studies used radiographic progression as the primary outcome, although with various definitions.
The value of RF as a prognostic marker in patients with EA was reportedly heterogeneous and extremely dependent on the prevalence of radiographic progression in the cohorts. Depending on the studies, positive predictive values (PPVs) of RF for radiographic progression ranged from 20% to 92%, without a clear trend towards one or the other of these extreme values. Negative predictive values (NPVs) were better, with half of the studies reporting a NPV of RF for radiographic progression between 60% and 80%, and the other half reporting even higher NPVs (80–100%). PPVs of ACPAs for radiographic progression in patients with EA were also heterogeneous, with approximately half of the studies reporting low PPVs with values between 20% and 40%, and the other half reporting high PPVs with values over 80%. On the other hand, NPVs of ACPAs for radiographic progression were high, around 80% in the majority of the included studies.
According to four of the studies, testing (and interpreting) the combined results of RF as well as ACPAs did not provide added benefit to the prognostic value of RF or ACPAs alone.56 ,59–61 We retrieved three studies reporting an influence of autoantibody titres on radiographic progression.24 ,25 ,57 In two studies, classifying patients by ACPA titres revealed a dose–response relationship between increased baseline ACPA titres and radiographic progression.25 ,57 In the third study, structural damage at 2 years (Larsen scores) was significantly higher when baseline RF titres were high as compared with low or absent.24
Two studies of multibiomarker disease activity (MBDA) assessment were retrieved.78 ,79 The correlation of the MBDA score with radiographic progression was weak (OR per unit of increase: close to 1.0 (1.0 to 1.1)). The association of higher (>44) MBDA scores and radiographic progression was better (OR vs low score 3.9 (1.0 to 14.3)), but, while the NPV for this cut-off was high (97%), the PPV did not exceed 20%; and thus MBDA scores appear to be of minor value for clinical practice.
One study investigated the value of anti-CarP antibodies.68 In this study, the prognostic value of anti-CarP was similar to that of anti-CCP antibodies.
Our search did not identify studies on the prognostic value of ESR and CRP level in patients with EA.
Imaging tests
Included studies evaluated mainly baseline hands and feet X-rays (six studies), with different radiological parameters according to the studies (van der Heijde-modified total Sharp score, joint erosions, BMD loss) (see online supplementary materials S6).47 ,58–60 ,72 ,75
Structural damage on baseline X-rays of hands and feet was associated with further radiographic progression, with particularly high NPVs (around 90%). This suggests that in the absence of baseline structural damage the likelihood of further erosive evolution is low. PPVs of baseline X-rays were reportedly low (around 30%) but this should be nuanced by the low prevalence of the outcome in the cohorts.
Other studies evaluated MRI (one study80) and US (three studies64 ,81 ,82). Given the available data in these studies, it was difficult to assess the predictive values of these imaging tests in patients with EA. The US studies were conducted using various parameters, outcomes and populations, and therefore the clinical relevance of US as a marker of prognosis in patients with EA appeared to be limited thus far. Power–Doppler (PD) at baseline seemed to be the most relevant US parameter, with an OR for the prediction of an increase in the erosion sharp score ≥5 at 1 year of 1.2 (1.0 to 1.4) per unit of increase in the PD score (scale 0–3 for each joint).81 Only one MRI study was included,80 reporting an increase of only 10% (OR 1.1 (1.0 to 1.2)) in the risk of radiographic progression (change in Genant-modified Sharp score >3 units) at 1 year for every increase of 5 units in the bone oedema MRI score (scale 0–90).
Studies addressing the prognostic value of other imaging modalities (scintigraphy, positron emission tomography) were not found.