The role of static bone histomorphometry in diagnosing renal osteodystrophy

Bone biopsy is the gold standard test to diagnose renal osteodystrophy (ROD). There is a preference to perform bone biopsy during renal transplantation but tetracycline bone labelling is usually not possible. We aimed to test if histomorphometry static parameters can identify low and high bone turnover as assessed by dynamic measurement using double tetracycline labelling.43 CKD stages 4-5D had trans-iliac bone biopsy using a 4 mm Jamshidi trephine and needle after tetracycline labelling. Quantitative histomorphometry was performed using the Bioquant Osteo histomorphometry system. Normal bone turnover was defined as bone formation rate/bone surface (BFR/BS) of 18-38 μm3/μm2/year. Static parameters of bone turnover included osteoblast surface/bone surface (Ob.S/BS, %), osteoclast surface/bone surface (Oc.S/BS, %) and erosion surface/bone surface (ES/BS, %). Receiver operating characteristics (ROC) analysis was used to evaluate diagnostic accuracy of these static parameters for low and high bone turnover (based on BFR/BS).Median (IQR) for BFR/BS in this study was 32.12 (17.76-48.25) μm3/μm2/year. 26% of patients had low, 34% had normal and 40% had high bone turnover. The area under the ROC curve (AUC) for Ob.S/BS, Oc.S/BS and ES/BS were non-significant indicating poor accuracy for identifying low bone turnover. The AUC for Ob.S/BS was 0.697 (95% CI 0.538 to 0.827) indicating fair accuracy for identifying high bone turnover. Oc.S/BS and ES/BS had non-significant AUCs for high bone turnover.Static histomorphometry parameters for bone turnover are unable to replace dynamic parameter in diagnosing ROD. Tetracycline bone labelling is still required.