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.