Point-of-care ultrasound (POCUS) performed in the pediatric emergency department has high accuracy in identifying hip effusion, the hallmark that distinguishes septic arthritis from other conditions, according to findings from a study featured in the Annals of Emergency Medicine.
The diagnosis of septic arthritis in pediatric patients is challenging, as the presenting symptoms can be nonspecific (e.g., limp, hip pain). As septic arthritis is an emergent, time-sensitive condition, identifying an effective approach for the diagnosis of the condition in children in an emergency department setting is critical.
The presence or absence of hip joint effusion can aid in diagnosing or ruling out septic arthritis; however, hip joint effusion requires ultrasound to identify.
A team led by Ruchika Mohla Jones, MD, of the Department of Pediatric Emergency Medicine at Connecticut Children's Hospital in Hartford, CT, investigated the accuracy of POCUS in pediatric emergency departments (PEDs) in identifying hip effusion to diagnose septic arthritis of the hip through a multicenter prospective study in five centers in the U.S. and Australia from October 2019 to October 2023.
Children ages 18 and younger who presented to the PEDs and whose clinical presentation necessitated radiology-performed ultrasound (RADUS) for a hip effusion were eligible. Participants received both POCUS by pediatric emergency physicians credentialed to perform hip ultrasound and RADUS of both hips, with the RADUS used as the reference standard in diagnosing hip effusion. The PED doctors categorized their POCUS findings as “yes” or “no” for the presence of hip effusion.
The study enrolled a total of 161 participants, with 322 hips scanned. The most frequent presenting symptoms reported were limp (39.8%) and joint pain (43.4%). In the five participating emergency departments, 18 credentialed pediatric emergency physicians enrolled patients and performed hip POCUS, with the number of physicians per site ranging from one to six. The median number of participants enrolled per physician was four (ranging from 1 to 49). Three physicians at high-volume centers were responsible for enrolling 99 (61.5%) of the 161 participants, including 53 (72.6%) of the 73 true positive cases. All measurements were taken by the pediatric emergency physicians who made the final determination of the presence of effusion.
In total, POCUS identified 77 hip effusions among the 74 participants (74 were symptomatic; three were asymptomatic), of which 75 (97.4%) were in agreement with RADUS. For the three high-volume pediatric emergency physicians, POCUS had a sensitivity of 98.1% and a specificity of 97.8%. For the other doctors, the POCUS sensitivity was 83.3%; specificity, 97.4%.
For the per-hip analysis, POCUS had a sensitivity of 89.3% and a specificity of 99.2%. For the per-participant analysis, effusions diagnosed using POCUS in 72 of the effusions diagnosed using POCUS (97.3%) of the 74 patients were in agreement with RADUS findings. POCUS had a sensitivity of 93.5% and a specificity of 97.6%.
RADUS identified 82 effusions in 77 participants (77 symptomatic, 5 asymptomatic), diagnosing hip effusions on the right side in 43 of the 77 (55.8%) participants and bilaterally in five (6.5%) participants. POCUS had a sensitivity of 97.3% and specificity of 94.3% for the symptomatic hip effusions.
Seven of the participants (4.3%) in the study underwent hip joint aspiration. Of the 77 participants with hip effusions on RADUS, six were diagnosed with Lyme disease (5 with unilateral hip effusion, 1 with bilateral); two were diagnosed with septic arthritis of the hip, both with unilateral effusions. In both instances of septic arthritis, POCUS accurately identified the effusions, in agreement with RADUS. Of the six participants presenting with bilateral symptoms, POCUS identified bilateral hip effusions in three, in accordance with the reference standard RADUS.
However, there were discrepancies between POCUS and RADUS concerning nine participants, which were taken to expert review. While some of the discrepancies were false negatives due to errors in POCUS image acquisition, there were also errors due to RADUS measurements that did not meet diagnostic criteria.
“Although the reference standard of RADUS reported by a radiologist used in the study was pragmatic and reflected real-world clinical practice, it highlighted that there is variability in reporting the presence of a hip effusion even among radiologists,” the authors wrote.
Furthermore, they noted that none of the participants with discrepancies between POCUS and RADUS underwent joint aspirations or had clinically significant pathology.
The authors suggested that future studies should further investigate the diagnostic accuracy of POCUS with physicians with different levels of ultrasound experience in diverse settings, and that POCUS be incorporated into an algorithm for the diagnosis of pediatric septic arthritis.
Read the study here.
