Validation of Septic Knee Monoarthritis Prediction Rule in a Lyme Disease Endemic Area

Retrospective validation of a rapid Lyme fluorescent immunoassay in differentiating Lyme arthritis from other musculoskeletal presentations in children in a Lyme-endemic region

Lyme arthritis can present similarly to other causes of joint pain and swelling including septic arthritis and other acute and chronic arthropathies of childhood. Septic arthritis, although rare, constitutes an orthopedic emergency and requires early surgical intervention to reduce the risk of permanent joint damage. Currently, results of standard serologic tests to diagnose Lyme disease take days to weeks, which is unhelpful in acute clinical decision-making. Thus, some children with Lyme arthritis are treated empirically for septic arthritis undergoing unnecessary invasive procedures and hospital admission while on inappropriate antibiotic therapy. We retrospectively validated the Quidel Sofia Lyme Fluorescent Immunoassay, a rapid serologic assay that can detect IgG and/or IgM antibodies to Borrelia burgdorferi in 10 minutes, in residual serum samples collected from 51 children who had Lyme arthritis and 55 children with musculoskeletal presentations who were Lyme negative. The sensitivity and specificity of the Sofia IgG to identify cases of Lyme arthritis in children were 100% (95% confidence interval [CI] of 93.0%-100%) and 96.4% (95% CI: 87.5%-99.6%), respectively. The positive likelihood ratio (LR) was 27.5 (95% CI 7-107), and the negative LR was 0.00 (95% LR 0.00-0.15). We propose that the Sofia IgG, a rapid method for identifying Lyme arthritis, may be useful in differentiating Lyme arthritis from other forms of arthritis. Used in conjunction with readily available clinical and laboratory variables, it could help to rapidly identify children who are at low risk of septic arthritis in Lyme-endemic regions.

IMPORTANCE

Lyme arthritis is a common manifestation of Lyme disease in children, with clinical features overlapping with other causes of acute and chronic joint pain/swelling in children. We have demonstrated that the Sofia IgG is a reliable test to rule in and rule out the diagnosis of Lyme arthritis in children with musculoskeletal presentations in a Lyme-endemic region. When used in conjunction with clinical and laboratory variables routinely considered when differentiating Lyme arthritis from other diagnoses, the Sofia IgG has the potential to fill an important gap in care, especially when acute decision-making is necessary. The Sofia IgG should be included in prospective research studies examining clinical prediction tools to identify children at low risk of septic arthritis.

Utility of Synovial Fluid Biomarkers for Culture-Positive Septic Arthritis in a Lyme Disease-Endemic Region

OBJECTIVE

To evaluate the performance of synovial fluid biomarkers to identify children with culture-positive septic arthritis.

METHODS

We identified children 6 months to 18 years old presenting to a single emergency department between 2007 and 2022 undergoing evaluation for septic arthritis defined by having a synovial fluid culture obtained. Our primary outcome was septic arthritis defined by a positive synovial fluid culture. We evaluated the ability of synovial fluid biomarkers to identify children with septic arthritis using area under the receiver operating characteristic curve (AUC) analyses. We measured the sensitivity and specificity of commonly used synovial fluid biomarkers.

RESULTS

We included 796 children, of whom 79 (10%) had septic arthritis. Compared with synovial white blood cell count (AUC, 0.72; 95% confidence interval [CI], 0.65-0.78), absolute neutrophil count (AUC, 0.72; 95% CI, 0.66-0.79; P = 0.09), percent neutrophils (AUC, 0.66; 95% CI, 0.60-0.71; P = 0.12), and glucose (AUC, 0.78; 95% CI, 0.67-0.90; P = 0.33) performed similarly, whereas protein (AUC, 0.52; 95% CI, 0.40-0.63, P = 0.04) had lower diagnostic accuracy. Synovial fluid white blood cell count ≥50,000 cells/μL had a sensitivity of 62.0% (95% CI, 50.4%-72.7%) and a specificity of 67.0% (95% CI, 63.4%-70.4%), whereas a positive synovial fluid Gram stain had a sensitivity of 48.1% (95% CI, 36.5%-59.7%) and specificity of 99.1% (95% CI, 98.1%-99.7%) for septic arthritis.

CONCLUSIONS

None of the routinely available synovial fluid biomarkers had sufficient accuracy to be used in isolation in the identification of children with septic arthritis. New approaches including multivariate clinical prediction rules and novel biomarkers are needed.

Surgical (over) treatment of pediatric Lyme arthritis: a need for faster Borrelia testing

Pediatric Lyme arthritis is described but not well-characterized in urban populations. Similarities in clinical features between Lyme and septic arthritis also results in some patients with Lyme arthritis undergoing surgical treatment. The aims of this study are to (1) characterize Lyme arthritis in an urban population and (2) determine what factors predispose patients with Lyme arthritis to undergoing surgery. We performed a retrospective review of children with Lyme arthritis at a single academic institution in New York City from 2016 to 2021. Inclusion criteria were age ≤18 years, involvement of a major joint, and positive Lyme serology. Patients treated with irrigation and debridement were compared to those treated non-surgically using Chi-squared tests with a significance of P  < 0.05. A total of 106 children with Lyme arthritis were included. Mean age was 9.5 years; 61.3% were male, and 71.7% were Caucasian. 46.2% lived in regions with an average household income >$100 000; 70.8% had private insurance. Ten patients (9.4%) underwent surgery for suspected septic arthritis. The operative group was more likely to have an elevated heart rate, white blood cell count, C-reactive protein level, erythrocyte sedimentation rate level and synovial cell count ( P  < 0.05). Patients were more likely to undergo surgery if they presented to the emergency department than to the clinic ( P  = 0.03). The average time for a Lyme test to result was 43.5 h, averaging 8.7 h after the surgical start time. Lyme arthritis occurs commonly in an urban pediatric population. Surgery is performed in ~10% of Lyme arthritis patients. More efficient diagnostic tests may reduce this rate.

Pediatric musculoskeletal infections

PURPOSE OF REVIEW

The aim of this article is to review the recent guidelines and literature regarding the diagnosis and the treatment of common pediatric musculoskeletal infections: septic arthritis, osteomyelitis, pyomyositis, and Lyme disease.

RECENT FINDINGS

In the last decade, a better understanding of the causative organisms of common bacterial infections, including Kingella , leads to prompt targeted antimicrobial coverage in all musculoskeletal infections. Prompt diagnosis and treatment continues to be the mainstay in the treatment of children with osteoarticular infections. Efforts to improve early detection have lead to improving rapid lab diagnostic testing; however, more advanced diagnostics such as arthrocentesis for septic arthritis and MRI for osteomyelitis and pyomyositis, remain the gold standard. Shorter and narrowed antibiotic courses, with appropriate transition to outpatient oral treatment provide effective infection clearance and reduction in complications of disease.

SUMMARY

Advances in diagnostics, including pathogen identification as well as imaging continues to improve our ability to diagnose and treat these infections, although still lack ability to provide definitive diagnosis without more invasive nor advanced techniques.

Lyme Arthritis

Arthritis is the most common late manifestation of Borrelia burgdorferi infection in the United States, usually beginning months after the tick bite. In most patients with Lyme arthritis (LA) today, arthritis is the presenting manifestation of the disease. Patients have swelling and pain in one or a few large joints, especially the knee. Serologic testing is the mainstay of diagnosis. Responses to antibiotic treatment are generally excellent, although a small percentage of patients have persistent, postinfectious synovitis after 2 to 3 months of oral and IV antibiotics, which respond to anti-inflammatory therapies. Herein we review the clinical presentation, diagnosis, and management of LA.