Association of explanatory factors with ARLA.
| Clinical Characteristics | Univariate Analysis | Multivariable Analysis | |
|---|---|---|---|
| Primary or Secondary | Analysis of Primary | Primary Explanatory | |
| Explanatory Variable | Explanatory Variables, n = 237 | Variables Plus Secondary Treatment Factors, n = 237 | |
| Unadjusted OR (95% CI) | Adjusted OR1 (95% CI) | ||
| Demographics | |||
| Age ≥ 10 yrs | 3.5 (1.8–6.7) | 2.5 (1.1–5.6) | 3.0 (1.2–7.3) |
| Male sex | 0.8 (0.4–1.6) | – | – |
| Clinical features at presentation | |||
| Acute migratory arthritis | 1.8 (0.9–3.7) | – | – |
| Prior, self-resolving episodes of joint swelling | 0.5 (0.3–1.1) | – | – |
| Continuous joint symptoms for at least 6 weeks | 13.9 (4.0–48.6) | 9.4 (2.5–34.7) | 8.0 (2.0–31.9) |
| Severe phenotype2 | 0.2 (0.1–0.5) | 0.4 (0.2–0.9) | 0.4 (0.2–0.99) |
| ≥ 9 bands on Western blot | 1.2 (0.6–2.5) | – | – |
| ≥ 2 active joints | 0.1 (0.03–0.5) | – | – |
| Arthritis limited to knee(s) | 5.6 (1.7–18.9) | 5.1 (1.4–19.2) | 4.9 (1.3–19.4) |
| Premature IAGC injection | 3.9 (0.5–28.4) | – | – |
| Clinical features within first 6 weeks after treatment initiation | |||
| Clinical worsening on treatment3 | 5.0 (1.9–13.1) | 4.2 (1.4–12.6) | 4.5 (1.4–14.2) |
| Features of SpA4 | 1.9 (0.2–21.5) | – | – |
| Presence of chronic joint changes5 | 0.5 (0.2–1.3) | – | – |
| Exploratory treatment characteristics | |||
| Dose of first antibiotic course too low6 | 4.0 (1.2–14.6) | – | 7.3 (1.4–37.3) |
| Documented treatment non-adherence7 | 4.0 (0.8–20.2) | – | 2.4 (1.1–5.3) |
↵1 Multivariable logistic models including all independent variables shown.
↵2 Unexplained fever, severe pain, hospitalization for severe pain, or measured ESR ≥ 40 mm/h.
↵3 Massive effusion, rupture of joint capsule or popliteal cyst, or symptomatic joint recruitment after antibiotic initiation.
↵4 (1) Presence of inflammatory back pain, enthesitis (tenderness at bony insertions of tendons and ligaments), tendonitis, or dactylitis; or (2) personal history of psoriasis, inflammatory bowel disease, or acute anterior uveitis.
↵5 (1) Flexion contracture > 20° or presence of flexion contracture without massive effusion; (2) muscle atrophy proximal to involved joint; (3) hypertrophy of femoral condyles; (4) joint erosions on imaging.
↵6 Antibiotic dose of first course too low per treatment guidelines3,4.
↵7 Treatment non-adherence defined as reported consumption of < 80% of prescribed antibiotic doses. ARLA: antibiotic-refractory Lyme arthritis; IAGC: intraarticular glucocorticoid; SpA: spondyloarthritis; ESR: erythrocyte sedimentation rate.