Ab0131 Not All That Hurts Is Fibromyalgia: The Challenge of Differential Diagnosis in Patients With a Pre-Existing Diagnosis or a Clinical Suspicion for Fibromyalgia

Background: The differential diagnosis of chronic widespread pain is very intricate, considering all of the possible causes of pain, for example rheumatic and musculoskeletal diseases (RMDs), neuropathy, myopathy/myositis, infections and vaccinations. Fibromyalgia (FM) is a complex syndrome characterised by a wide range of different symptoms. In recent years the diagnostic workup has become clearer, using the 2016 ACR revised criteria. Interestingly, the previous recommendations concerning diagnostic exclusions were eliminated and so a diagnosis of FM did not exclude the presence of other diseases. Objectives: To explore the outcome of the diagnostic process in a cohort of patients with a previous diagnosis of FM or with a clinical suspicion of FM. Methods: Patients at first referral to our institution with previous diagnosis of FM or with a clinical suspicion of FM between 2020 and 2023 were retrospectively assessed. Reason for referral was classified as follows: Group 1) Patients reporting a previous FM diagnosis, Group 2) Patients being referred by another physician due to clinical suspicion of FM, Group 3) Patient spontaneously requesting a consultation due to personal concerns about having FM. All comorbidities at first referral, including RMDs, were recorded and patients were reclassified according to the confirmation of pre-existing diagnosis, new FM/RMD diagnosis, or other alternative diseases. Results: A total of 145 patients were included in the study, 25 (17%) in Group 1, 86 (59) in Group 2 and 34 (23%) in Group 3 (Figure 1A). Patients who self-referred for FM were significantly younger and with less RMD comorbidities compared to those referred by a physician. Overall, 114 (79%) patients were reclassified as having FM (either confirmed pre-existing diagnosis or new diagnosis) (Figure 1B) and they had significantly higher scores of VAS pain, VAS fatigue, WPI, SSS compared to those reclassified as no FM. Table 2 also shows the new RMD diagnosis in the 2 groups and the additional non RMD diagnosis. Group 1: Overall, FM diagnosis was confirmed in 23 (92%) patients. Of the 21 patients with a previous diagnosis of FM but not of an RMD, 15 (71%) were FM-confirmed with no new RMD diagnosis. Conversely, 4 (19%) were FM-confirmed and also diagnosed with an RMD and 1 (5%) was FM not confirmed and diagnosed with an RMD and 1 (5%) was FM not confirmed with no new RMD diagnosis. Group 2: Overall, 67 (78%) of the 86 patients referred with a clinical suspicion of FM were actually diagnosed with FM. Among these 86 patients, 60 had no previous diagnosis of RMD. 25/60 (42%) were diagnosed only with FM, 23/60 (38%) were diagnosed with both FM and an RMD, 4/60 (7%) were diagnosed with and RMD but not with FM, 8/60 (13%) were diagnosed neither with FM nor with an RMD. Group 3: Overall, 24 (70%) of the 34 patients self-referred with a clinical suspicion of FM were actually diagnosed with FM whereas 8 (23%) patients were diagnosed neither with FM nor with an RMD and 2 (6%) patients were diagnosed with an RMD but not with FM. When comparing the demographic and clinical features, including for example the WPI and the SSS of patients from Group 2 and 3 that were diagnosed with FM only or FM + RMD we did not observe any differences that could have allowed to predict who would classify as FM only or FM + RMD. Conclusion: Our findings underline the importance of making a precise differential diagnosis. Physicians need to be more rigorous when evaluating chronic pain, and should also take into account the fact that a diagnosis of FM does not exclude a concomitant co-morbidity. Interestingly, a significant number of patients, mainly of younger age, seems to be capable of identifying clinical red flags suggesting FM. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.