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Joint Fluid Cell Count in Acute Bacterial Arthritis Patients Proven Positive Culture in Children
Yuto Otsubo1, Meiwa Shibata1,2, Hiroshi Hataya3
1From the Division of Infectious Diseases.
Insights
Most pediatric acute bacterial arthritis cases confirmed by joint fluid culture have fewer than 50,000 white blood cells (WBCs) per cubic millimeter. This finding challenges the traditional diagnostic threshold for this serious pediatric infection.
Area of Science:
- Pediatric infectious diseases
- Rheumatology
- Microbiology
Background:
- Acute bacterial arthritis (ABA) is a significant pediatric infection with potential for long-term motor impairments.
- A joint fluid white blood cell (WBC) count exceeding 50,000 cells/mm³ is typically used for presumptive ABA diagnosis.
- The diagnostic utility of this WBC count threshold requires further evaluation in pediatric populations.
Purpose of the Study:
- To assess the effectiveness of joint fluid WBC counts in diagnosing pediatric ABA.
- To compare actual joint fluid WBC counts with the established diagnostic threshold of 50,000 cells/mm³.
Main Methods:
- Retrospective review of electronic medical records for pediatric patients diagnosed with ABA between March 2010 and March 2023.
- Inclusion criteria required confirmed ABA via positive joint fluid culture for a pathogenic organism.
- Data collected included demographics, arthrocentesis timing, culture results, and joint fluid WBC counts.
Main Results:
- Twenty-two pediatric patients with confirmed ABA were included in the study.
- The median joint fluid WBC count was 19,575 cells/mm³, significantly below the 50,000 cells/mm³ threshold.
- Only 23% of patients met or exceeded the 50,000 cells/mm³ criterion, indicating a low sensitivity of this threshold.
Conclusions:
- The conventional joint fluid WBC count threshold of 50,000 cells/mm³ is not met by the majority of pediatric ABA cases confirmed by culture.
- Rethinking diagnostic criteria for pediatric ABA may be necessary, considering lower WBC counts.
- Early diagnosis and treatment of pediatric ABA remain critical to prevent motor comorbidities.
Background:
Acute bacterial arthritis (ABA) is a serious, pediatric infection that can result in motor comorbidities. Normally, a joint fluid white blood cell (WBC) count of 50,000 or more cells/mm 3 is used to make a presumptive diagnosis of ABA. This study evaluated the utility of the joint fluid WBC count for diagnosing pediatric ABA confirmed by a positive culture result.
Methods:
Patients with ABA between March 2010 and March 2023 at Tokyo Metropolitan Children's Medical Center were included. ABA was confirmed by positive joint fluid culture results for a pathogenic organism. Patients with negative results and those without a joint fluid WBC count were excluded. Electronic medical records were retrospectively reviewed for demographic data, timing of arthrocentesis, culture results and the joint fluid WBC count.
Results:
Ninety-five patients with ABA were identified; of these, 22 were included. The median age was 5 years [interquartile range (IQR): 2-10 years]. Males comprised 55% of the population. The median joint fluid WBC count was 19,575 (IQR: 6806-47,388) cells/mm 3 , and 23% of the patients had 50,000 cells/mm 3 or more. The median time from symptom onset to arthrocentesis was 3 days (IQR: 2-5 days). The isolated organisms were methicillin-susceptible Staphylococcus aureus (50%), methicillin-resistant S. aureus (9%), Streptococcus pyogenes (27%), Streptococcus pneumoniae (5%), Klebsiella pneumoniae (5%) and Salmonella spp. (5%).
Conclusions:
Most of the patients with ABA confirmed by positive results of a joint fluid culture had a joint fluid WBC count of less than 50,000 cells/mm 3 .
