Evaluation of a biomagnetic technique for measurement of orocaecal transit time

To evaluate a novel non-invasive and harmless biomagnetic technique to measure orocaecal transit time.

A biomagnetic method was employed to measure orocaecal transit time in 26 healthy volunteers, 12 patients presumed to have rapid small intestine transit and six volunteers with slow intestinal transit induced by loperamide. Results were compared to those obtained with a standard H2 breath test performed simultaneously.

Subjects ingested a test meal consisting of a chocolate-flavoured custard (120 g, 120 kcal) containing 18 g of lactulose and 3 g of ferrite powder as a magnetic tracer. External measurements of the magnetic signal on the caecal area and determination of H2 concentrations on samples of end-expiratory air were performed at 5-10-min intervals for 4 h after test meal ingestion.

The biomagnetic method yielded reliable values for orocaecal transit time in all healthy volunteers and 11 out of 12 patients with diarrhoea, whereas the H2 test was uninterpretable in two volunteers and five patients, because of either high fasting H2 levels or absolute lack of H2 excretion. Transit time values determined by the biomagnetic method (mean +/- SD = 93 +/- 32 min) were generally higher than those assessed by H2 breath analysis (77 +/- 22 min). Thus, although results obtained by the two methods were significantly correlated (R = 0.56, P < 0.01), calculated agreement between them was poor. Nevertheless, the two methods were equally effective in detecting both abnormally fast transit associated with diarrhoea and slow transit induced by loperamide.

The simple and harmless biomagnetic technique for measuring orocaecal transit time is as effective as the H2 breath test in detecting abnormal transit rates, and may provide reliable measurements in circumstances where H2 breath profiles are uninterpretable.