Introduction: Dual-energy x-ray absorptiometry (DXA) is the most widely diagnostic technique used to assess bone mineral disease (BMD) in kidney transplant (KT) patients. It is uncertain if DXA reflects the real bone status of these patients. Bone microindentation (BMI) is a new technique that involves measuring the distance that a narrow needle penetrates the anterior face of shinbone and therefore the bone strength to a micro-trauma and the bone mechanical characteristics. Our aim was to analyze BMD in a cohort of long-term KT patients with blood parameters, radiological study and BMI.

Methods: Cross sectional study with 27 long-term (>10 years) KT patients. Bone markers, lumbar spine X-ray, DXA and BMI performed in all patients.

Results: Mean age was 63.1 ± 10.3 years. 55.6% were male. Median time postKT was 14.3 years. Mean body mass index 26.1 Kg/m2. 67% had received anti-lymphocyte induction therapy, 96.3% calcineurin-inhibitors, 74.1% antimetabolites and 25.9% mTOR-inhibitors. All patients had initially received steroids, but 78% of them underwent steroid withdrawal at a median time of 16 months postKT. 30% had received extra steroid doses (cumulative dose 77 mg/kg/year). Mean eGFR-MDRD was 42.6 ml/min with 24h-proteinuria of 305 mg. 85.2% of patients had 25-OHvitamin-D<30 and 51.9% PTH>120. Only two patients had asymptomatic fractures in radiography. Mean T-score by DXA was -1.6 (lumbar), -1.2 (total hip), -1.73 (femoral neck). Bone strength by BMI was 81 ± 7.4 microns. We did not observe a statistically relation between DXA values and BMI values. There were no differences between patients on steroids vs those steroid-free, neither a correlation with cumulative steroid dose.

Conclusions: KT patients with more than 10 years of follow-up had similar bone mineral density values by DXA and bone strength by BMI to general population (matched by age and gender). As expected, there was no correlation between DXA and BMI values. BMI is a real technique that allows to measure bone strength to micro-fracture and could enable to analyze bone mineral situation of KT patients in larger prospective studies.

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