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Distinguishing Lyme from Septic Arthritis in Children
Abstract & Commentary
By Hal B. Jenson, MD, FAAP, Professor of Pediatrics, Tufts University School of Medicine; Chief Academic Officer, Baystate Medical Center, Springfield, MA, is Associate Editor for Infectious Disease Alert.
Dr. Jenson is a speaker for Merck.
Synopsis: A retrospective review of 179 cases of acute monoarticular arthritis in children revealed that the clinical similarities between Lyme arthritis, suppurative arthritis, and other causes of arthritis do not permit reliable discrimination by the clinician using clinical or laboratory criteria.
Source: Thompson A, et al. Acute pediatric monoarticular arthritis: Distinguishing lyme arthritis from other etiologies. Pediatrics. 2009;123:959-965.
A retrospective cross-sectional review was conducted in children ≥ 18 years of age presenting with acute monoarticular arthritis who underwent arthrocentesis at Boston Children's Hospital emergency department between December 2000 and September 2006. A total of 179 eligible patients were studied, including 46 (26%) with suppurative arthritis, 55 (31%) with lyme arthritis, and 78 (43%) with another etiology. The organisms identified by culture as causing suppurative arthritis included Staphylococcus aureus (31), group A Streptococcus (4), Streptococcus pneumoniae (2), Neisseria gonorrhea (1), Neisseria meningitidis (1), Enterococcus (1), Salmonella (1), group B Streptococcus (1), Haemophilus influenzae (1), Haemophilus parainfluenzae (1), and Actinomyces (1). The majority of patients with lyme disease (84%) did not recall tick exposure.
Patients with lyme arthritis were more likely to have knee involvement (p < 0.001), a history of a tick bite (p = 0.02), and less likely to have a history of fever (p < 0.001) or fever (≥: 38.0°C) at presentation (p < 0.01). Patients with lyme arthritis also had lower erythrocyte sedimentation levels (p < 0.01), C-reactive protein levels (p < 0.001), joint white blood cell counts (p < 0.03), and joint neutrophil percentages (p < 0.001). Multivariate analysis showed that knee involvement was a positive predictor (odds ratio: 12 [95% CI: 2.8-47]) of lyme arthritis and that history of fever (odds ratio: 0.22 [95% CI: 0.051-0.91]) and elevated C-reactive protein level (odds ratio: 0.79 [95% CI: 0.68-0.93]) were negative predictors of lyme arthritis. Amodel with these three factors had a Hosmer-Lemeshow value of 0.78, sensitivity of 88%, and specificity of 82%.
Distinguishing acute monoarticular suppurative arthritis from lyme disease in endemic areas is a common clinical problem. There are over 60,000 new cases of lyme disease each year, with over 60% of these occurring among children 5-14 years of age. lyme arthritis is a late manifestation of lyme disease. As expected, 51% of cases of lyme arthritis presented outside the tick season of June through October.
Lyme arthritis is characterized by a wide range of laboratory abnormalities, including peripheral white blood cell counts, erythrocyte sedimentation rate levels, C-reactive protein levels, and joint white blood cell counts. The wide range of these values observed with lyme arthritis precludes using these laboratory tests to distinguish lyme arthritis from suppurative and other forms of arthritis.
The clinical differential of suppurative arthritis from lyme arthritis continues to be difficult. The early diagnosis of suppurative arthritis is important to facilitate early drainage and prevent articular damage. The model from these data is not sufficiently powerful to permit use to distinguish lyme arthritis from suppura tive arthritis in individual patients; with a sensitivity of 88% and specific of 82%, this model would only accrately identify 41 of 46 patients with suppurative arthritis. Clinicians in lyme-endemic areas need to consider both lyme disease and suppurative arthritis as potential etiologies in children presenting with acute monoarticular arthritis, regardless of the time of year at presentation.