Concordance and precision of dual X-ray absorptiometry with a 10 s scan.

Development of dual energy X-ray absorptiometry (DXA) scanners with multidetector array technology has resulted in greatly shortened scanning times. The Hologic QDR-4500 includes an ultrafast (10 s) "turbo" scan mode recommended by the manufacturer for fast screening studies or as an aid to positioning the patient prior to scanning using the normal fast (30 s), medium (1 min) or high definition (2 min) modes. The suitability of the turbo mode for use in routine clinical studies was assessed by examining the concordance of bone mineral density (BMD) measurements obtained in this mode with measurements obtained using the three normal scanning modes. Studies in 151 female patients showed statistically significant discrepancies in four out of the six scan sites studied with systematic differences of 2.9% and 3.1% being observed for the posteroanterior (PA) spine and intertrochanteric region of the hip, respectively. In vivo precision for the 10 s scan found by performing duplicate measurements on 37 patients had a coefficient of variation of 1.3% for PA spine and 2.5% for femoral neck BMD. An investigation of the dependence of precision on body mass index (BMI) shows that the precision of spine and hip BMD was adversely affected with increasing BMI but the trend was statistically significant only in the spine. It was concluded that turbo mode scans are acceptable for routine clinical studies of the spine and hip but should not be used for longitudinal studies or patients with BMI greater than 30 kg m-2.

Failure of soybean trypsin inhibitor to exert deleterious effects in calves.

To evaluate nutritional effects induced in calves by feeding soybean trypsin inhibitor, 16 calves were fed 1) raw soybeans, 2) heated soybeans, 3) heated soybeans plus soybean trypsin inhibitor, 4) heated (raw soybeans plus soybean trypsin inhibitor). Ration 1 caused depression of growth and reduced digestibility of protein and fat as compared to Ration 2. No differences were significant in calves fed Rations 3 and 4. The weights and enzymatic activities of pancreas were similar in all groups. Soybean trypsin inhibitor plays a minor role, if any, in calf nutrition.