#4551 DEVELOPMENT OF AN X-RAY–BASED BONE OXALOSIS GRADING SCALE TO ASSESS OXALATE ACCUMULATION IN PATIENTS WITH PRIMARY HYPEROXALURIA TYPE 1

Abstract Background and Aims Primary hyperoxaluria type 1 (PH1) is a rare genetic disease in which hepatic oxalate overproduction can lead to kidney stones, nephrocalcinosis, failure, systemic oxalosis, condition calcium deposited various tissues, including bone [1]. Radiological signs of oxalosis include findings such as dense metaphyseal bands coarse trabeculation [2]. No scale exists grade severity using X-rays. Method An X-ray grading evaluate specific bones was developed based on expert opinion. Scores individual items ranged from 0–4, except for ribs spine, 0–2. Higher values represent more advanced oxalosis. To validate the scale, 85 images 5 pediatric patients with PH1 who had were collected charts at Shaare Zedek Medical Center de-identified Two blinded, independent raters evaluated each twice assigned applicable item scale. Inter-rater intra-rater reliability analyses conducted weighted Cohen's kappa asymptotic 95% confidence intervals (CIs) estimate interpreted proposed literature [3]. Total estimates generated by pooling all observed ratings across items. Results overall inter-rater (0.83 [95% CI: 0.79, 0.87]) (0.95 [0.93, 0.97]) demonstrated almost perfect agreement. Overall >0.8 1.0 (almost agreement) left hand/wrist, hip, knee (femur), humerus; >0.6 0.8 (substantial right (tibia), humerus, ribs; >0.4 0.6 (moderate (femur) (fibula). The (fibula) poor agreement (−0.08 [−0.27, 0.10]). hand/wrist (tibia) considered unreliable due lack variability data, standard errors not estimable. Calculable spine Most other could be calculated because kappas one or both lacked variability. In these instances, first second moderate (>0.4 1.0; [femur], [tibia], ribs). For (fibula), −0.14 (−0.34, 0.05) 1.00, respectively, they 1.00 0.00. Conclusion We novel X-ray–based PH1. strength reliable estimates. removed reliability.