SO07118F-SODIUM FLUORIDE POSITRON EMISSION TOMOGRAPHY AND BONE HISTOMORPHOMETRY - COMPARISON BETWEEN ONLY BONE TURNOVER -BASED AND EXPERT EVALUATION -BASED CLASSIFICATION OF RENAL OSTEODYSTROPHY

Abstract

Abstract Background and Aims The diagnosis and the differentiation of renal osteodystrophy (ROD) are challenging. Bone biopsy is the golden standard, but it is invasive and not available in every center. Bone turnover rate is defined by bone formation rate and/or activation frequency. Adynamic bone disease is defined as low turnover bone with reduced osteoblast- and osteoclast activities. Hyperparahyreoid bone disease or osteitis fibrosa is defined as high turnover bone with osteoclast- and osteoblast activities and fibrosis. 18F- Sodium Fluoride positron emission tomography (18F-NaF PET) is a noninvasive imaging technique that allows assessment of regional bone turnover. The aim was to assess how well bone turnover –based classification of ROD correlates with the classification determined by an expert histomorphometrist (HK), and how these correlate with 18F-NaF PET analysis Method A total of 24 dialysis patients underwent a 18F-NaF PET scan. Fluoride activity was measured at the anterior iliac crest and in the lumbar region. An iliac crest bone biopsy was obtained within 4 weeks from the PET-scan. The diagnosis of bone histomorphometry was determined based on turnover-mineralization-volume (TMV) classification. Firstly, bone turnover was assessed using bone formation rate and activation frequency. Secondly, also other histomorphometric parameters (eg. osteoid volume, osteoid surface, resorption surface, mineralized surface, osteoblast and osteoclast surfaces and peritrabecular fibrosis) were also taking into account for classification of ROD by a histomorphometrist. Results Based on bone turnover parameters only, 12% of the patients had high turnover and 64% low turnover. When the diagnosis of renal osteodystrophy was made by a histomorphometrist, 40% had hyperparathyreoid bone/osteitis fibrosa and 24% adynamic bone disease or ostemalasia. 18F-NaF PET´s sensitivity to recognize hyperparathyreoid bone disease was 80% end specificity 100% (cut-of value 0.055).18F-NaF PET´s sensitivity to recognize adynamic bone disease was 100% and specificity 61% (cut-of value of fluoride-activity 0.038) Conclusion 18F-NaF PET works well as a diagnostic tool, when the diagnosis of ROD is based on the histopathological evaluation. It remains unknown how variations in normal bone turnover rate can be detected in CKD patients by 18F-NaF PET and if treatment decisions of ROD can be made only based on bone turnover.