A total of 203 consecutive patients with IBD were recruited, with 26 individuals being excluded from the study because of a previous diagnosis of SpA or other RMDs. The remaining 177 out of 203 participants who completed the DETAIL and IBIS-q questionnaires were enrolled in the study (Fig. 1). Out of the 177 patients, 92 (52.0%) had UC and 85 (48.0%) had CD. The mean age was 48.4 years (standard deviation (SD) ± 17.2), and 73 (41.2%) were female. The mean duration of IBD was 8.2 years (SD ± 5.9). Patient features, including ongoing therapies, are summarized in Table 2.

Flowchart of patients enrolled in the study. IBD inflammatory bowel disease

In 10 out of 177 patients (5.6%), a new diagnosis of IBD-related arthritis was established, and all patients fulfilled the ASAS criteria for axial or peripheral SpA, based on clinical involvement. The median duration of musculoskeletal symptoms before the diagnosis of IBD-related arthritis was 4 months (IQR 1.8–10.5) (Table 3).

Imaging-confirmed enthesitis was the predominant pattern in 8 out of 10 cases axial involvement in 1 out of 10 cases, and peripheral arthritis in 1 out of 10 cases (Fig. 1).

The median LEI and SPARCC were 1 (IQR 1–2) and 2 (IQR 1–3), respectively.

Among the 8 cases with imaging-confirmed enthesitis as predominant pattern, 8 out of 8 lacking concomitant peripheral synovitis but in 2/8 (25%) entheseal swelling was present, the mean CRP was 0.6 (+ 0.4) mg/dl, the mean morning stiffness was 21.0 (+ 24.9) mins, and the median number of imaging active entheseal sites was 2 (IQR 1–3). The most frequent entheseal site involved was lateral epicondyle of the humerus, followed by Achilles tendon and quadriceps tendon (Fig. 2).

Sites of ultrasound confirmed enthesitis at the diagnosis of IBD-related arthritis

CD was the main IBD pattern in this group of patients (7/10 cases). The endoscopic disease activity measured by SES-CD for CD and MAYO for UC revealed that 5/10 (50%) patients exhibited remission at the rheumatological evaluation, 1 presented mild disease activity, and 4 presented at least moderate disease activity.

Seven out 10 newly diagnosed patients with IBD-related arthritis were not concomitantly treated with conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) or biologic disease-modifying antirheumatic drugs (bDMARDs) for IBD during the rheumatological assessment. None of the newly diagnosed patients with IBD-related arthritis were receiving vedolizumab [23].

Among the 177 patients surveyed, 55 individuals (31.1%) showed positive results in either the DETAIL or IBIS-q questionnaires. Specifically, 5 patients (9%) tested positive solely in the DETAIL questionnaire, 26 patients (47.3%) were positive only in the IBIS-q, and 24 patients (43.7%) tested positive in both questionnaires.

Within the remaining 122/177 patients with a negative questionnaire, 29 (16.4%) exhibited a score of 2 for both DETAIL and IBIS-q; while a score of 1 was present in 36/177 (20.3%) and 32/177 patients (18.1%) in DETAIL and IBIS-q, respectively; ultimately no positive answers were present in 83/177 (46.9%) for DETAIL and 66/177 (37.2%) for IBIS-q.

The DETAIL questionnaire demonstrated a sensitivity of 40.0% (95% CI 12.2–73.8%) and a specificity of 84.4% (95% CI 78.0–89.6%) for diagnosing IBD-related arthritis, yielding a LR+ of 2.6 and a LR− of 0.7 (Table 4). On the other hand, the IBIS-q questionnaire (using a cutoff of ≥ 3) exhibited a sensitivity of 70.0% (95% CI 34.8–93.3%) and a specificity of 74.3% (95% CI 66.9–80.7%), with a LR+ of 2.7 and a LR− of 0.4 (Table 4).

Of 177 patients, 48 presented at least one positive questionnaire (cutoff score ≥ 3) without IBD-related arthritis diagnosis. The alternative diagnoses were osteoarthritis in 27 out of 48 cases (56.6%), followed by not otherwise specified arthralgia in 10 out of 48 cases (20.1%), fibromyalgia in 6 out of 48 cases (12.5%), myofascial pain in 3 out of 48 cases (6.25%), and non-inflammatory low back pain in 2 out 48 cases (4%) (Fig. 3).

Alternative diagnosis in patients with at least one positive questionnaire. OA osteoarthritis, NOSA not otherwise specified arthralgia, FM fibromyalgia, MP myofascial pain, NILBP non-inflammatory low back pain