#6641 bone material strength index and dual energy x-ray absorptiometry in evaluation of bone health in autosomal polycystic kidney disease

Abstract Background and Aims Bone material strength measured with the use of impact microindentation technique (OsteoProbe®) has emerged recently as potentially beneficial tool in evaluating bone quality in metabolic bone disorders. Patients with autosomal polycystic kidney disease (ADPKD) carry an increased risk of skeletal complications, both due to deficiency of polycystins and development of chronic kidney disease-mineral bone disorder (CKD-MBD). In our preliminary study, we found that bone material strength index (BMSi) associated with bone mineral density (BMD) measured with the use of dual energy X-ray absorptiometry (DXA) in chronic kidney disese patients (CKD). The aim of the present study was to find if the same applies to patients with ADPKD. We evaluated bone health by measuring BMSi and performing DXA in patients with ADPKD. Method BMSi was measured (OsteoProbe®, Active Life Scientific, USA) in 64 adult patients (37 men, mean age 43 years) with ADPKD in CKD stages G1-4. The measurement of BMSi compared the resistance to impact of microindentation in bone and reference material. After applying local anaesthesia, we impacted the cortical bone in the midshaft tibia in 10 different points. BMD was measured using Hologic Discovery Wi densitometer in multiple sites: lumbar spine, hip, 1/3 distal non-dominant forearm and whole-body. Trabecular bone score (TBS) was calculated using Medimaps TBS iNsight software. Results Mean values of BMSi, TBS and BMD are presented in the Table 1. BMSi in ADPKD patients was lower than average value observed in healthy individuals (85 men and 80 women). A positive linear relationship between BMSi and BMD was found in all of the examined sites with the highest standardized regression coefficient for 1/3 distal forearm (R2 = 0.315, beta = 0.57, p < 0.001) and weakest for lumbar spine (R2 = 0.003, beta = 0.33, p = 0.003). There was no association between BMSi and TBS. Conclusion This is the first report on BMSi in ADPKD patients. In agreement with the notion of a distinct bone phenotype in ADPKD, we observed a median bone material strength index in patients with ADPKD that was lower than the reference value. BMSi associated with BMD, but not with TBS. However, the association with BMD overall is weak, with BMD explaining only 3 to 31% of the variability of BMSi. This observation suggests complementarity and warrants additional studies investigating whether BMSi associates with hard bone endpoints, independent of BMD.