Toxic shock in children with bone and joint infections: a review of seven years of patients admitted to one intensive care unit

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.

The role of real-time PCR testing in the investigation of paediatric patients with community-onset osteomyelitis and septic arthritis

BACKGROUND

Culture yield in osteomyelitis and septic arthritis is low, emphasising the role for molecular techniques.

AIMS

The purpose of this study was to review the laboratory investigation of childhood osteomyelitis and septic arthritis.

METHODS

A retrospective review was undertaken in an acute tertiary referral paediatric hospital from January 2010 to December 2016. Cases were only included if they had a positive culture or bacterial PCR result from a bone/joint specimen or blood culture, or had radiographic evidence of osteomyelitis.

RESULTS

Seventy-eight patients met the case definition; 52 (66%) were male. The median age was 4.8 years. Blood cultures were positive in 16 of 56 cases (29%), with 11 deemed clinically significant (Staphylococcus aureus = 8, group A Streptococcus = 3). Thirty-seven of 78 (47%) bone/joint samples were positive by culture with S. aureus (n = 16), coagulase-negative Staphylococcus (n = 9) and group A Streptococcus (n = 4), being the most common organisms. Sixteen culture-negative samples were sent for bacterial PCR, and four were positive (Kingella kingae = 2, Streptococcus pneumoniae = 1, group A Streptococcus = 1).

CONCLUSIONS

Sequential culture and PCR testing can improve the detection rate of causative organisms in paediatric bone and joint infections, particularly for fastidious microorganisms such as K. kingae. PCR testing can be reserved for cases where culture is negative after 48 h. These results have been used to develop a standardised diagnostic test panel for bone and joint infections at our institution.

Hip Synovial Fluid Cell Counts in Children From a Lyme Disease Endemic Area

BACKGROUND

Patients with septic hip arthritis require surgical drainage, but they can be difficult to distinguish from patients with Lyme arthritis. The ability of synovial fluid white blood cell (WBC) counts to help discriminate between septic and Lyme arthritis of the hip has not been investigated.

METHODS

We assembled a retrospective cohort of patients ≤21 years of age with hip monoarticular arthritis and a synovial fluid culture obtained who presented to 1 of 3 emergency departments located in Lyme disease endemic areas. Septic arthritis was defined as a positive synovial fluid culture result or synovial fluid pleocytosis (WBC count ≥50 000 cells per µL) with a positive blood culture result. Lyme arthritis was defined as positive 2-tiered Lyme disease serology results and negative synovial fluid bacterial culture results. All other patients were classified as having other arthritis. We compared median synovial fluid WBC counts by arthritis type.

RESULTS

Of the 238 eligible patients, 26 (11%) had septic arthritis, 32 (13%) had Lyme arthritis, and 180 (76%) had other arthritis. Patients with septic arthritis had a higher median synovial fluid WBC count (126 130 cells per µL; interquartile range 83 303-209 332 cells per µL) than patients with Lyme arthritis (53 955 cells per µL; interquartile range 33 789-73 375 cells per µL). Eighteen patients (56%) with Lyme arthritis had synovial fluid WBC counts ≥50 000 cells per µL. Of the 94 patients who underwent surgical drainage, 13 were later diagnosed with Lyme arthritis.

CONCLUSIONS

In Lyme disease endemic areas, synovial fluid WBC counts cannot always help differentiate septic from Lyme arthritis. Rapid Lyme diagnostics could help avoid unnecessary operative procedures in patients with Lyme arthritis.