Correlation between 18F-Sodium Fluoride positron emission tomography and bone histomorphometry in dialysis patients

Background: The diagnosis of renal osteodystrophy is challenging. Bone biopsy is the gold standard, but it is invasive and limited to one site of the skeleton. The ability of biomarkers to estimate the underlying bone pathology is limited. F-18-Sodium Fluoride positron emission tomography (F-18-NaF PET) is a noninvasive quantitative imaging technique that allows assessment of regional bone turnover at clinically relevant sites. The hypothesis of this study was, that F-18-NaF PET correlates with bone histomorphometry in dialysis patients and could act as a noninvasive diagnostic tool in this patient group. Methods: This was a cross-sectional diagnostic test study. 26 dialysis patients with biochemical abnormalities indicating mineral and bone disorder were included. All the participants underwent a F-18-NaF PET scan and a bone biopsy. Fluoride activity in the PET scan was measured in the lumbar spine and at the anterior iliac crest. Dynamic and static histomorphometric parameters of the bone biopsy were assessed. As histomorphometric markers for bone turnover we used bone formation rate per bone surface (BFR/BS) and activation frequency per year (Ac.f). Results: There was a statistically significant correlation between fluoride activity in the F-18-NaF PET scan and histomorphometric parameters such as bone formation rate, activation frequency and osteoclast and osteoblast surfaces and mineralized surfaces. F-18-NaF PET'S sensitivity to recognize low turnover in respect to non-low turnover was 76% and specificity 78%. Because of the small number of patients with high turnover, we were unable to demonstrate significant predictive value in this group. Conclusions: A clear correlation between histomorphometric parameters and fluoride activity in the F-l8-NaF PET scan was established. F-18-NaF PET may possibly be a noninvasive diagnostic tool in dialysis patients with low turnover bone disease, but further research is needed.