A34: Seeing the Forest Through the Trees: Predictors of Inflammatory Causes of Joint Pain in New Patients
Authors: Millman Perel , Pilossyan Lilit , Kimura Yukiko , Weiss Jennifer E. , Nyirenda Themba , Janow Ginger L. 
Published: March 2014

Background/Purpose:

Joint pain is one of the most common reasons for referral to pediatric rheumatology clinics throughout the world. Typically, these patients ultimately fall into one of three categories of diagnosis: (1) Inflammatory, (2) Non‐Inflammatory, or (3) mechanical, with each category requiring different subspecialty care and follow‐up. Our objective was to determine what factors on clinical history best predict the final etiology of the joint pain in three major categories, inflammatory, non‐inflammatory, and mechanical.

Methods:

Patients between ages of 2 and 22 seen by the pediatric rheumatology clinic at Hackensack University Medical Center between the dates of 1/1/2005 and 6/30/2006 reporting joint pain were included in our retrospective chart review. Data was collected regarding demographics, symptom history, physician assessment, and patient assessment. Final diagnosis as determined by the treating physician was categorized as one of the three previously stated categories. A category logistic analysis for nominal data was performed using the mechanical/overuse category in the response as the reference category.

Results:

621 patients were included in the analysis, with a median age of 11.5 years. 63.9% of the patients included were female. 54.1% were diagnosed with an inflammatory cause, 25.8% with a mechanical cause, and 20.1% with a non‐inflammatory cause. Patients with inflammatory causes were more likely to be younger than those with non‐inflammatory causes (OR 1.171, p < 0.0001). Patients with a longer duration of symptoms (>3 months) were less likely to have an inflammatory cause for their pain (OR 0.105, p < 0.0001). Those with inflammatory etiology were more likely to have a fever (OR 13.107, p < 0.0119), swelling (OR 5.865, p < 0.0001) and limp (OR 1.827, p < 0.0024) than those with mechanical or non‐inflammatory causes of their pain, but overall had lower reported pain scores than patients with non‐inflammatory causes (OR 1.342, p < 0.0001). Patients with non‐inflammatory causes of joint pain were significantly more likely to be home schooled than those with either mechanical causes or inflammatory causes (OR 4.858, p < 0.0102). On multivariate analysis association of the diagnosis with potential risk factors revealed significant differences in final diagnostic category based on gender, age and patient visual analogue score. Those diagnosed with non‐inflammatory causes were more likely to be female (OR 18.714, p < 0.0089), older (OR 1.480, p < 0.0038) and to report higher visual analogue scores (OR 1.653, p < 0.0088).

Conclusion:

The most significant predictors of final diagnosis category were gender, age and patient reported VAS. However, there were multiple other factors that appear important in predicting final diagnosis. Patients with inflammatory joint pain such as JIA tend be younger at presentation, have a shorter duration of symptoms and are less likely to complain of pain. These symptoms, along with signs of arthritis on exam should prompt quick referral to a pediatric rheumatologist. Patients with non‐inflammatory pain that is so debilitating that patients can't attend school should also be evaluated by a rheumatologist as they may have fibromyalgia.