1. The rate of gastric emptying was measured directly in 14 convalescent hospital patients and paracetamol absorption was studied following an oral dose of 1.5 g.2. Rapid gastric emptying was associated with the early appearance of high peak plasma paracetamol concentrations whereas peak concentrations were low and occurred late when gastric emptying was slow.3. There was a significant correlation between the rate of gastric emptying and the 0-4 and 0-24 h urinary excretion of paracetamol and its metabolites.4. In five patients with abnormally slow gastric emptying the mean maximum plasma concentration and 0-4 and 0-24 h urinary excretion of paracetamol were significantly lower than in seven patients with normal gastric emptying rates while the time taken to reach maximum plasma concentrations was longer.5. Individual differences in the rate of gastric emptying may contribute to variable absorption of many drugs.

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The effect of intramuscular pethidine or diamorphine on gastric emptying and the absorption of orally administered paracetamol was assessed in eight normal subjects. 2 Both drugs produced a significant and striking delay in gastric emptying and absorption of paracetamol. 3 It seems inevitable that pethidine and diamorphine will retard the absorption of other orally administered drugs.

OBJECTIVE: To investigate whether the dual-energy X-ray absorptiometry (DEXA) was a better predictor of abdominal fat, measured by magnetic resonance imaging (MRI) at the level of L2-L3, than anthropometric measurements in non-obese men and non-obese women. DESIGN: Observational, cross sectional study. SUBJECTS: 34 healthy subjects (17 men and 17 women) aged 20 ± 53 y with a body mass index (BMI)`30 kgam 2 . MEASUREMENTS: Fat distribution parameters including waist circumference and waist-to-hip ratio (WHR); intra abdominal fat (IAF) by MRI; and central abdominal fat (CAF) by DEXA. RESULTS: Measurement of IAF by MRI, was highly correlated to the CAF measured by DEXA. In men, both waist circumference and WHR had similar correlation to IAF as DEXA. In women, waist circumference was less well correlated with IAF than DEXA, and the WHR had a weaker non signi®cant correlation with IAF. CONCLUSIONS: In non obese men; DEXA, waist circumference and WHR can predict IAF equally well, while in non obese women, DEXA is superior to waist circumference and much better than WHR.

Measurements of whole-body bone mineral made by Hologic, Lunar and Norland dual-energy X-ray absorptiometers have been compared. It was found that in each case the results were changed by new software protocols introduced by the manufacturers during the course of the study. With a moderately anthropomorphic model, the later software corrected some anomalies of regional bone mineral content (BMC) observed earlier. There was some slight dependence of total BMC on thickness and fat proportion and up to 15% difference between instruments. Measurements on volunteers showed good precision, but there were differences between instruments made by different manufacturers. There were high correlations, but the slopes of regression lines suggested differences of calibration of up to 8%; the standard errors of the estimates were 110 to 190 g. with maximum deviations from regression of 17%. There were regional disparities in BMC, particularly in the trunk, which arise (in part at least) from the imposition of a higher bone threshold by Hologic. From the pattern of results it was concluded that different assumptions were made by the manufacturers, particularly concerning the fat distribution model, which preclude the interchangeability of results from different instruments.

SUMMARY Gastric emptying was studied in 12 diabetic patients, six with and six without objective evidence of autonomic neuropathy and in 20 non-diabetic controls, using a double isotope scintiscanning technique which differentiated between solid and liquid emptying. Three patients with autonomic neuropathy exhibited gastric stasis, although this was detected by conventional radiology in only one. Neither the patients with stasis nor those without exhibited abnormally rapid early gastric emptying. In patients without stasis, the normal differentiation between solid and liquid emptying was impaired, suggesting an abnormality of antral peristalsis not attributable to vagal denervation. Both intravenous and oral metoclopramide produced symptomatic improvement in two patients with gastric stasis and restored their gastric emptying to normal.

For an eating disorder study over a period of 1 year, we measured total-body bone mineral using a Hologic QDR 1000W in a total of 157 subjects and observed anomalies that questioned the accuracy of such measurements. Using the recommended Enhanced software, a change in total bone mineral content (⌬BMC) correlated positively with a change in weight (⌬W; r ‫؍‬ 0.66), but a loss of weight was associated with an increase in bone mineral areal density (BMD; r ‫؍‬ 0.58), arising from a reduction in bone area (AREA). Both regressions were highly significant. The dominant factor in this relationship was a strong correlation between ⌬AREA and ⌬BMC, for all parts of the skeleton, r > 0.9, with a slope close to 1. This is implausible because bone area would not be expected to change. When Standard software was used, the slope of the ⌬BMC/⌬W correlation was steeper, but the ⌬BMD/⌬W regression became positive. An artefact of dual-energy X-ray absorptiometry processing was suspected, and phantom measurements were made. The phantom consisted of tissue-equivalent hardboard cut and stacked to form cylinders corresponding to the head, trunk, arms, and legs of a standard man. The skeleton was constructed from layers of aluminium sheet as an approximation of the average shape, BMD, BMC, and AREA in each region. When aluminium thickness was varied, BMD thresholds were found, approximately 0.4 g/cm 2 for the legs and 0.2 g/cm 2 for the arms. Above these, bone area rose fairly rapidly toward a plateau. At higher skeletal densities, the relationships between measured and true BMDs were close to linear, but slopes were less than unity, so that changes would be underestimated by 10 -30%. Increases of thickness of the soft tissue of the phantom lowered AREA slightly. Uniform fat proportion increases led to decreases in BMC and AREA, but lard wrapped in an annulus around the limbs led to spurious increases in BMC and AREA of a similar magnitude to those observed in vivo, while BMD fell slightly, although there had been no true change of bone variables. Similar results were obtained with lard around the limbs of a volunteer. Reanalysis of phantom scans using Standard software confirmed the software differences noted in vivo. The phantom measurements offer an explanation of the anomaly in vivo and demonstrate that, under different circumstances, change in both BMC and BMD can be wrongly recorded. We believe that no valid conclusions can be drawn from measurements by the Holgic QDR 1000W of bone changes during weight

Errors in spinal dual X-ray absorptiometry (DXA) were studied by analysing X-ray CT scans taken for diagnostic purposes on 20 patients representing a wide range of fat content. The mean difference between the fat thickness over the vertebral bodies and that over a background area in antero-posterior (AP) scanning was 6.7 +/- 8.1 mm for men and 13.4 +/- 4.7 mm for women. For lateral scanning the mean fat thickness difference was only 4 mm for both sexes, but the dispersion was greater, with a standard deviation of 15 mm. To relate these differences to errors in bone mineral, measurements were made of the bone mineral equivalence of fat-equivalent materials on DXA machines from three manufacturers. 10 mm of adipose tissue was equivalent to -0.043 g/cm2 of hydroxyapatite. For AP scanning a non-uniform fat distribution leads to a mean overestimate of 0.029 g/cm2 for men and 0.057 g/cm2 for women. The error exceeded 0.1 g/cm2 in 10% of slices. For lateral scanning the error exceeded 0.1 g/cm2 (about 15% of normal) in a quarter of slices.