1. INTEROBSERVER AND INTRAOBSERVER VARIABILITY IN THE C-EOS. COMPARISON BETWEEN EXPERIENCED SPINE SURGEONS AND TRAINEES. María del Mar Pozo-Balado, PhD José María López-Puerta, MD Marco Antonio Pérez-Gañán, MD David M Farrington, MD

2. INTRODUCTION Describe and group patients to guide optimal care and prognosticate outcomes within Early Onset Scoliosis (EOS) children. Substantial to excellent inter-observer reliability has been demonstrated in experienced surgeons.  Early Onset Scoliosis Classification System (C-EOS) Intra-observer reproducibility and Intra- and inter-observer reproducibility by clinicians with different level of expertise.  However, in order to expand it use, it must also show…

3. OBJECTIVE To demonstrate that C-EOS classification is a highly reliable comparison tool in EOS patients regardless of the reviewers level of training.

4. PATIENTS AND METHODS I Agreement study. Two expert spine orthopedic surgeons and two senior year orthopedic residents comparison of 81 cases of EOS classified according to the C-EOS classification on two separate occasions.  Study Design  C-EOS classification Williams BA, et al., J Bone Surg Am. 2014

5. PATIENTS AND METHODS II  Inter-observer agreement. Comparison between the initial responses of all evaluators. Interclass correlation coefficients (ICC) for continuous variables (age). Kappa indexes (Ik) for categorical variables (Etiology, Cobb Angle and Kyphosis). Levels of agreement for ICC and Ik: 0.00-0.2, slight agreement; 0.21-0.40, fair agreement; 0.41-0.60, moderate agreement; 0.61-0.8, substantial agreement; 0.81-1.00, almost perfect agreement. Landis and Koch, Biometrics 1977  Patients. 81 children under 10 years old. Complete clinical data. Available radiographic studies.

6. PATIENTS AND METHODS III  Intra-observer agreement. Comparison between 2 evaluations of the same cases by the same evaluator, separated by 72 hours. Interclass correlation coefficients (ICC) for continuous variables (age) Kappa indexes (KI) for categorical variables (Etiology, Cobb Angle and Kyphosis). Levels of agreement for ICC and k: 0.00-0.2, slight agreement; 0.21-0.40, fair agreement; 0.41-0.60, moderate agreement; 0.61-0.8, substantial agreement; 0.81-1.00, almost perfect agreement. Landis and Koch, Biometrics 1977  Sensitivity and Specificity Sensitivity: fraction of positive cases correctly classified by the evaluators, expressed as percentages (true-positive assessments). Specificity: true-negative assessments.

7. RESULTS I  Demographical and Clinical data of the 81 study children. CharacteristicValue Age, median months [IQR]81 [44-107] Cobb, median angle [IQR]36 [29-55] Kiphosys, median angle [IQR]20 [15-25] Etiology n (%) Congenital37 (47.5) Idiopathic23 (28.4) Neuromuscular12 (14.8) Syndromic9 (11.1)

8. RESULTS II  Almost perfect intra-observer agreement variability. Classification variableExpert 1Expert 2Trainee 1Trainee 2 Age1.000* 0.983*1.000* Etiology 0.981** 0.924** 0.964** 0.982** Cobb 1.000** 0.975** 0.950** 1.000** Kyphosis 1.000** 0.931** 1.000** *ICC; **IK No significant differences were observed in the intra-observer agreement of age, ethiology, Cobb or kyphosis between experts and trainees.

9. RESULTS IV RESULTS III  Almost perfect inter-observer agreement variability in all cases except for etiology between experts. Classification variableExpertsTrainees Age0.999*0.983* Etiology 0.775** 0.874** Cobb 1.000** 0.950** Kyphosis 0.886** 1.000** *ICC; **IK No significant differences were observed in the inter-observer agreement of age, ethiology, Cobb or kyphosis between experts and trainees. Substantial inter-observer agreement for ethiology between experts.

10. RESULTS II RESULTS IV  Sensibility and Specificity rates for C-EOS classification according to the experience. EvaluatorSensibility (%)Specificity (%) Exp 1 10097.1 Exp 2 60 92.1 Trainee 1 97.6 91.7 Trainee 2 81.8 98.6

11. CONCLUSIONS Agreement between and within observers for the C-EOS Classification is very high. However, Etiology variable shows lower agreement than the rest of variables.