New ACR/EULAR criteria for pediatric CNO include bone pain lasting at least 6 weeks
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PHILADELPHIA — New classification criteria for pediatric chronic nonbacterial osteomyelitis include chronic bone pain or functional musculoskeletal limitation lasting 6 weeks or longer, according to a speaker at ACR Convergence 2022.
The new criteria come from the American College of Rheumatology and EULAR, and offer a roadmap for diagnosing or excluding chronic nonbacterial osteomyelitis (CNO), said Yongdong Zhao, MD, PhD, RhMSUS, assistant professor and director of ultrasound at Seattle Children’s Hospital and its Center for Clinical and Translational Research.
“Entry criteria is needed, as all of the other rheumatology classification criteria has indicated it is necessary for a case to meet all criteria to be considered,” Zhao told attendees.
According to Zhao, the new entry criteria additionally states that the patient’s age at the time of onset must be younger than 18 years and there must be abnormal radiographic or MRI findings at nonarthritic bone sites.
The list of exclusion criteria for CNO includes confirming evidence of a mutually exclusive mimicker, a platelet count of less than 100,000 per mm3, and abnormal serum LDH levels indicating a concern for malignancy, Zhao said.
Once the entry criteria are confirmed and the exclusion criteria are dismissed, 10 domains may be evaluated to indicate whether a patient is considered positive for CNO. Each domain is to be evaluated based on a point system. Patients who score 55 points or higher qualify as having CNO, Zhao said.
The domains
The presence of abnormal radiographic findings at specific bone sites is the first domain. If patients have abnormal findings at the mandible or clavicle, they score 18 points. Any time there are findings at nonspecific sites, without any findings at the most specific sites, the patient is scored 10 points.
“We know some of the sites, such as hands and neurocranium, are very unlikely to be in CNO,” Zhao, said. “These patients, if they have the least specific sites while they do not have any sites at the clavicle or mandible, they get zero points.”
Lesion distribution is the second-most weighted domain, according to Zhao. Patients with multifocal lesions with any symmetrical patterns score 16 points. Multifocal lesions without symmetrical patterns score eight points. In patients with unifocal lesions without whole body imaging, three points are scored. Finally, in patients with unifocal lesions who have had whole body imaging done, there are no points given.
“The symmetrical terminology, we continue to use it, but it refers really to more of a bilateral pattern,” Zhao, said.
The third domain deals with the patient response to antibiotic monotherapy.
“If a patient had complete response to an appropriate monotherapy, meaning no NSAIDs at the same time, that means no CNO,” Zhao said.
Meanwhile, patients with no available antibiotic data were given 13 points. Patients who had no or partial responses to antibiotic monotherapy receive 16 points.
Bone biopsy in review
The fourth domain evaluates bone pathology. In patients with no signs of inflammation or fibrosis in their bones, there were 0 points given. Patients with no biopsy received six points. Patients with only inflammation received 10 points, while those with signs of fibrosis get 12 points and patients with both get 13 points, Zhao said.
The next domain rheumatologists should evaluate is the age of the patient. Patients aged 3 years or younger receive 0 points, but patients aged 3 years or older get 13 points.
Coexisting conditions
Coexisting conditions is the next domain to be evaluated, according to Zhao. Patients without implicated conditions, or who have no data, receive zero points. Patients with axial arthritis without psoriasis, inflammatory bowel disease or rashes receive four points. Patients with rashes but no IBD receive eight points, while those with IBD receive nine points.
Anemia and fever are two other domains that must be evaluated. Patients with hemoglobin levels of less than 10 mg per dl receive zero points, while those with no information available receive three points and those with 10 or more mg per dl receive five points.
Patients who have a fever receive zero points. When there is no information on fevers available, they receive two points. In the absence of a fever they receive four points, Zhao said.
Erythrocyte sedimentation rate is the second to last domain for evaluation. Patients with 60 mm or more per hour receive zero points. In patients with no available data, they receive one point. Patients with a rate of less than 60 mm per hour get three points.
The final domain is serum C-reactive protein level. Levels of 30 mg per liter or greater get zero points. Patients with no available data get one point and patients with fewer than 30 mg per liter receive three points.
“We conclude that newly proposed ACR/EULAR classification criteria for pediatric CNO perform well to classify patients with CNO,” Zhao, said. “These are relatively easy, even if the patient has not had a bone biopsy, it will allow the researchers to develop a relatively homogenous cohort for further studies.”
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Zhao Y. Proposed ACR/EULAR classification criteria for pediatric CNO. Presented at: ACR Convergence 2022; Nov. 11-14, 2022; Philadelphia (hybrid meeting).
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