An evaluation of a test using 14C labelled triglyceride in the diagnosis of steatorrhoea

14C-triolein breath test as a rapid and convenient screening test for fat malabsorption

The 14C-triolein breath test was evaluated as a screening test for fat malabsorption in 50 consecutive patients. After the ingestion of a 30-g fat meal containing 5 microCi 14C-triolein, the breath excretion of 14CO2 was measured at hourly intervals for 6 h and compared with a 3-day faecal excretion of fat. Nineteen patients had steatorrhoea and 31 patients normal fat excretion. The maximum specific activity of CO2 in the breath provided the best means of distinguishing between the two groups, with no false-negative values and nine false-positive values (29%). Our findings confirm that the 14C-triolein breath test is sensitive and has sufficient specificity for screening fat malabsorption, especially among outpatients. If a normal 14C-triolein breath test is obtained, it seems unnecessary to perform measurements of excretion of faecal fat.

Estimation of 14C-triolein assimilation as a test of lipid assimilation. Breath test or measurement of serum radioactivity?

Two tests of lipid assimilation based on estimation of 14C-triolein assimilation from expiratory 14CO2 (breath test) and from serum radioactivity of 14C, respectively, were investigated in 48 consecutive patients suspected of having malassimilation. Patients with proven malassimilation had significantly lower expiration of 14CO2 and lower serum radioactivity of 14C than patients with normal lipid assimilation. The se-14C test correctly diagnosed significantly more patients with malassimilation than the breath test; the diagnostic efficiencies were 0.87 and 0.74, respectively. The results of both tests correlated with measurement of faecal fat. However, within the group of patients with proven malassimilation the results of the breath test correlated poorly with faecal fat, whereas a significant correlation was found between the se-14C test and faecal fat within this group. Correspondingly, the correlation between the results of the breath test and the se-14C test was poor, indicating that intermediate metabolism influences the results.

Comparison of simple screening tests for fat malabsorption

Three tests were evaluated as screening procedures for fat malabsorption--namely, measurement of serum optical density, serum triglyceride concentration, and 14CO2 breath excretion after the administration of a 60 g fat meal containing 10 muCi glycerol tri[1-14C]oleate. The results of these tests were compared with fat excreted in a three-day faecal collection after adjustment for completeness of collection as assessed by using non-absorbable radio-opaque markers. Fifty-two patients with various symptoms and eight normal subjects were studied. The maximum increase in serum optical density or triglyceride concentration above the fasting value discriminated poorly between subjects with normal and increased adjusted faecal fat excretion. In contrast, seven- or eight-hour cumulative 14CO2 breath excretion provided good discrimination with only four (7%) false-positive and no false-negative results. The simplicity and convenience of breath analysis make it an attractive alternative to analysis of faecal fat excretion in screening for fat malabsorption.

The glyceryl [14C]tripalmitate breath test: a reassessment

Several reports have been published commending the use of 14C-labelled triglyceride breath tests in the assessment of fat malabsorption. We report further studies using gyceryl [14C]tripalmitate. Corrections for age, weight or metabolic rate failed to improve the test's ability to discriminate between malabsorbers and control subjects. A correction for respiratory quotient improved the linear correlation observed between the breath test results and daily faecal fat excretion. The significance of these findings is discussed and a number of problems identified which, at present, are preventing the introduction of breath tests for fat malabsorption into routine clinical practice.

Vitamin-B12 status of patients on long-term metformin therapy

Vitamin-B(12) malabsorption has been found in 21 (30%) of 71 diabetic patients taking long-term metformin therapy in addition to dietary management. The patients with evidence of B(12) malabsorption had significantly lower haemoglobin levels (and significantly higher serum folic acid levels) than those with normal B(12) absorption. Steatorrhoea was found in only one patient. Stopping metformin therapy resulted in reversion of B(12) absorption to normal in most patients examined. Four patients with B(12) malabsorption were found to have pathologically low serum B(12) levels. The causes and implications of these findings are discussed and it is concluded that all patients on long-term metformin therapy should have annual serum B(12) estimations.