Is dual-energy absorptiometry accurate in the assessment of bone status of patients with chronic kidney disease?

Several patients with chronic kidney disease (CKD) have deteriorated bone status. Estimation of bone status using DXA has limitations especially in patients with CKD accompanying aortic calcifications. Quantitative CT and the trabecular bone score could be more accurate methods to estimate bone status for patients with CKD and vascular calcifications. INTRODUCTION: It remains unclear whether dual-energy absorptiometry (DXA) is appropriate for the assessment of bone status in patients with chronic kidney disease (CKD), a disease that impacts bone health. The aims of this study were to compare DXA and central quantitative computed tomography (cQCT) and to evaluate bone status in patients with pre-dialysis CKD. METHODS: This retrospective study included 363 healthy control subjects whose bone mineral density (BMD) was evaluated with DXA and 117 CKD patients whose BMD was evaluated using both cQCT and DXA. Diagnostic discordance was assessed between the lumbar spine (LS) and femur neck (FN) from DXA or between two modalities. The trabecular bone score (TBS) was extracted from DXA images. The volume of abdominal aortic calcification (AAC) was calculated using CT images from cQCT. RESULTS: Using LS DXA T-score, osteoporosis was less common in the CKD group than in controls. Patients with normal LS BMD using DXA were reclassified into osteopenia or osteoporosis using cQCT in CKD patients. Among discordant subjects between FN and LS in DXA, a higher BMD of LS was more common in CKD patients than in controls. CKD patients had lower TBS than controls despite having the same diagnosis using DXA. AAC volume negatively correlated with BMD from cQCT and with TBS but not with BMD from DXA. CONCLUSIONS: TBS and cQCT could accurately assess bone status in CKD patients since DXA may overestimate LS BMD, likely due to an increased AAC volume.

Growth disturbance after lengthening of the lower limb and quantitative assessment of physeal closure in skeletally immature patients with achondroplasia.

This study evaluated the effect of limb lengthening on longitudinal growth in patients with achondroplasia. Growth of the lower extremity was assessed retrospectively by serial radiographs in 35 skeletally immature patients with achondroplasia who underwent bilateral limb lengthening (Group 1), and in 12 skeletally immature patients with achondroplasia who did not (Group 2). In Group 1, 23 patients underwent only tibial lengthening (Group 1a) and 12 patients underwent tibial and femoral lengthening sequentially (Group 1b). The mean lengthening in the tibia was 9.2 cm (59.5%) in Group 1a, and 9.0 cm (58.2%) in the tibia and 10.2 cm (54.3%) in the femur in Group 1b. The mean follow-up was 9.3 years (8.6 to 10.3). The final mean total length of lower extremity in Group 1a was 526.6 mm (501.3 to 552.9) at the time of skeletal maturity and 610.1 mm (577.6 to 638.6) in Group 1b, compared with 457.0 mm (411.7 to 502.3) in Group 2. However, the mean actual length, representing the length solely grown from the physis without the length of distraction, showed that there was a significant disturbance of growth after limb lengthening. In Group 1a, a mean decrease of 22.4 mm (21.3 to 23.1) (4.9%) was observed in the actual limb length when compared with Group 2, and a greater mean decrease of 38.9 mm (37.2 to 40.8) (8.5%) was observed in Group 1b when compared with Group 2 at skeletal maturity. In Group 1, the mean actual limb length was 16.5 mm (15.8 to 17.2) (3.6%) shorter in Group 1b when compared with Group 1a at the time of skeletal maturity. Premature physeal closure was seen mostly in the proximal tibia and the distal femur with relative preservation of proximal femur and distal tibia. We suggest that significant disturbance of growth can occur after extensive limb lengthening in patients with achondroplasia, and therefore, this should be included in pre-operative counselling of these patients and their parents.

Coronary heart disease risk assessment in diabetes mellitus: comparison of UKPDS risk engine with Framingham risk assessment function and its clinical implications.

AIMS: To assess differences between absolute coronary heart disease (CHD) risks calculated by Joint British Societies (JBS) risk calculator and UKPDS risk engine and its impact on CHD primary prevention management in diabetes mellitus (DM). METHODS: Seven hundred Type 2 DM patients without arterial complications were identified from nine general practices in the Scarborough area. Their absolute 10-year CHD risks were calculated. The differences in the proportion of patients identified for aspirin and statin under JBS and National Institute for Clinical Excellence (NICE) guidelines by these two methods were determined. The proportion of additional patients identified for statin in the Scarborough population as a consequence of CHD risk threshold reduction from 30 to 15% (as recommended by NICE) was also determined. RESULTS: UKPDS risk engine calculated significantly higher mean 10-year CHD risk (UKPDS vs. JBS, 21.5 vs. 18.3%, P < 0.0001). Both methods identified approximately 65% of patients to be eligible for aspirin and statin if NICE recommendations were followed. At a risk threshold of 30%, the UKPDS risk engine identified more patients for statin. Reducing the CHD risk threshold from 30 to 15% for statin initiation will identify an additional 0.5% of the total population for this treatment. CONCLUSIONS: Both methods are comparable in identifying at-risk patients under NICE recommendations. A high proportion has risk levels that merits primary CHD prevention. Lowering the risk threshold for statin treatment has a small numerical impact on the whole population.