Urine toxicology screening reduces misdiagnosis of cocaine-induced ANCA-positive disease as idiopathic granulomatosis with polyangiitis.

Objectives: Study aims were to assess the impact of urine cocaine screening in distinguishing cocaine-induced midline destruction lesions (CIMDLs) from idiopathic ANCA-associated systemic vasculitis (AASV), to evaluate the adoption and effectiveness of screening and to explore its clinical implications.

Methods: We conducted a retrospective single-centre case series, reviewing rheumatology patients with suspected new or relapsing AASV, ages 18-55 years, from April 2021 to July 2024. Patients were in two groups: an active screening group offering urinary cocaine testing for all patients and a standard care group, with ad hoc testing based on clinical suspicion. Demographics, clinical presentations and diagnostic pathways were analysed.

Results: Of 11 cases in the active screening group, all denied cocaine use, 7 were diagnosed with CIMDL from urine screening and 4 patients were treated for vasculitis. In the standard care group of 15 patients, 2 patients had CIMDLs (admitted cocaine use), no patients had urine screening and 13 were treated for AASV. In total, there were nine CIMDL cases [mean age 38.2 years (interquartile range 11; six females), most [7/9 (78%)] were from active screening. CIMDL presentations were heterogeneous, including vocal cord palsy, lymphadenopathy and cutaneous vasculitis. CIMDL cases were positive for perinuclear ANCA (6/9) and PR3 (7/9), with no MPO positivity, and 5/9 (71%) failed to provide an adequate initial urine sample. There were no formal complaints or concerns from screening.

Conclusion: These data support the effectiveness and acceptability of systematic screening for cocaine to improve the identification of CIMDLs, reducing misdiagnosis and unnecessary treatment. A protocol for systematic screening is proposed to improve the care for these patients.