Characteristics | Resolved < 3 mos, n = 188 | ARLA, n = 49 | p1 |
---|---|---|---|
Demographics | |||
Age, yrs, median (IQR) | 9.0 (6.9–11.8) | 11.6 (9.0–13.8) | < 0.0012 |
Age ≥ 10 yrs3 | 71 (38) | 33 (67) | < 0.001 |
Male sex3 | 121 (64) | 29 (59) | 0.50 |
Race | 0.05 | ||
White | 142 (76) | 45 (92) | |
Not white | 29 (15) | 2 (4) | |
Unknown race | 17 (9) | 2 (4) | |
Ethnicity | 0.114 | ||
Non-Hispanic | 158 (84) | 47 (96) | |
Hispanic | 8 (4) | 0 | |
Unknown ethnicity | 22 (12) | 2 (4) | |
Year of presentation to rheumatology clinic | 0.51 | ||
2000–2006 | 56 (30) | 17 (35) | |
2007–2013 | 132 (70) | 32 (65) | |
Specialty of clinician who diagnosed Lyme arthritis | < 0.0014 | ||
Primary care | 48 (26) | 29 (59) | |
Emergency medicine | 55 (29) | 5 (10) | |
Rheumatology | 52 (28) | 3 (6) | |
Orthopedics | 32 (17) | 12 (24) | |
Infectious diseases | 1 (1) | 0 | |
Seen by a pediatric rheumatologist within 1 week of antibiotic initiation | 67 (36) | 3 (6) | < 0.001 |
Days after antibiotic initiation to presentation in rheumatology clinic, median (IQR) | 21 (0–38) | 93 (41–131) | < 0.0015 |
Clinical presentation | |||
Acute migratory arthritis3 | 7 (4) | 0 | 0.354 |
Prior self-resolving episodes of joint swelling3 | 74 (39) | 13 (27) | 0.10 |
Continuous joint symptoms for at least 6 weeks3 | 4 (2) | 8 (16) | < 0.0014 |
Missing duration of baseline joint symptoms | 37 (20) | 17 (35) | 0.03 |
≥ 2 active joints3 | 51 (27) | 2 (4) | 0.001 |
Arthritis limited to knee(s)3 | 138 (73) | 46 (94) | 0.002 |
Arthritis limited to a single knee | 118 (63) | 44 (90) | < 0001 |
Severe phenotype3,6 | 109 (58) | 11 (22) | < 0.001 |
Unexplained fever | 46 (24) | 8 (16) | 0.23 |
Severe pain | 61 (32) | 3 (6) | < 0.001 |
Hospitalization for severe pain | 30 (16) | 3 (6) | 0.08 |
Measured ESR ≥ 40 mm/h | 66 (35) | 6 (16) | 0.01 |
Lyme Western blot IgG ≥ 9 bands3 | 140 (74) | 38 (78) | 0.66 |
HLA-B27–positive | 1 (1) | 0 | 0.304 |
Unknown HLA-B27 status | 162 (86) | 38 (78) | |
Premature IAGC injection3 | 2 (1) | 2 (4) | 0.194 |
Patient and family history | |||
History of previously treated Lyme disease | 12 (6) | 3 (6) | 0.994 |
History of known tick bite | 34 (18) | 8 (16) | 0.82 |
History of personal autoimmune disease | 3 (2) | 0 | 0.994 |
Family history of Lyme disease | 18 (10) | 9 (18) | 0.08 |
Family history of other autoimmune disease | 76 (40) | 24 (49) | 0.28 |
Features within 6 weeks of diagnosis | |||
Features of SpA3,7 | 2 (1) | 1 (2) | 0.504 |
Clinical worsening on treatment3,8 | 9 (5) | 10 (20) | 0.0014 |
Presence of chronic joint changes3,9 | 39 (21) | 6 (12) | 0.18 |
Dose of first antibiotic course too low | 5 (3) | 5 (10) | 0.044 |
Unknown dose of first antibiotic course | 16 (9) | 7 (14) | 0.284 |
First course of antibiotic with too low frequency10 | 17 (9) | 3 (6) | 0.774 |
Unknown frequency of first antibiotic course | 11 (6) | 6 (12) | 0.134 |
Documented treatment nonadherence11 | 3 (2) | 3 (6) | 0.114 |
Prescribed nonsteroidal antiinflammatories | 55 (29) | 14 (29) | 0.93 |
Values are expressed as n (%) unless otherwise indicated.
↵1 Calculated from chi-square test except where indicated.
↵2 Calculated from t test.
↵3 Primary explanatory variable.
↵4 Calculated from Fisher’s exact test.
↵5 Calculated from Wilcoxon rank-sum test.
↵6 Characteristics combined into 1 factor of severity in multivariable models.
↵7 Presence of inflammatory back pain, enthesitis, tendonitis, or dactylitis; personal history of psoriasis, inflammatory bowel disease, or acute anterior uveitis.
↵8 Massive effusion, joint capsule rupture, or symptomatic joint recruitment after antibiotic initiation.
↵9 Flexion contracture present or > 20° in the presence of massive effusion, proximal muscle atrophy, condylar hypertrophy, or erosions on imaging.
↵10 In all but 1 case, amoxicillin was given twice daily rather than 3 times daily, as recommended by treatment guidelines3,4.
↵11 Defined as taking < 80% of prescribed antibiotic doses. ARLA: antibiotic-refractory Lyme arthritis; ESR: erythrocyte sedimentation rate; IAGC: intraarticular glucocorticoid; IgG: immunoglobulin G; IQR: interquartile range; SpA: spondyloarthritis.