Clinical value of 14C-phenylacetic oil as a fat absorption test

A quantitative assessment of serum chylomicron by light scattering intensity: application to the intestinal fat absorption test

A novel fat absorption test to clarify the malabsorption syndrome was developed using a micronephelometric technique and compared with the classic conventional technique using 131I-triolein. An integrity of time-sequential light scattered from chylomicron-related turbidity in serum was determined between 0 and 300 min after butter fat load, being expressed in terms of the light scattering intensity (LSI). A good correlation was obtained between LSI and the serum level of chylomicron-triglyceride determined by an ultracentrifugation technique (r = 0.819, P < 0.001). The maximal LSI was consistently observed at 180 min after administration of a test meal in the normal group (n = 39), whereas the malabsorption syndrome group (n = 35) was distinctly different and could be further classified according to four patterns of LSI changes. In addition, an inverse correlation was found between this fat absorption test and the 131I-triolein absorption test. It was concluded that the micronephelometric technique which does not use a radionuclide is advantageous in its simple and safe evaluation of fat malabsorption syndrome.

The fat meal test of malabsorption: some further experience

A fat meal test was evaluated in 21 healthy controls, 14 pathological controls and 11 malabsorption patients. The amount of fat used was 1 g per kg body wt, and the time for the post-cibal blood sampling was 2 h after the start of the meal. Combining serum triglyceride determination and serum turbidity measurement, the malabsorption group was fully discriminated from the control groups.

Clinical value of dual-isotope fat absorption test system (FATS) using glycerol [125I]trioleate and glycerol [75Se]triether

In order to delineate the clinical value of a dual-isotope fat absorption test system (FATS) using glycerol [75Se]triether as lipid-phase marker and glycerol [125I]trioleate as the test lipid, fecal isotope ratios from single stools (and a 72-hr stool homogenate) were compared to quantitative fecal fat excretion. The study included 11 patients without and 24 patients with steatorrhea. With a figure of 0.8% as the upper limit of normal, the test was a reliable indicator of steatorrhea with 87.5% sensitivity and 81.8% specificity; efficiency was 85.7%. Related to a prevalence of steatorrhea of 45.9% as the mean value of 1269 consecutive 72-hr specimens investigated for steatorrhea during 1978-1982, the positive (negative) predictive value of the FATS is 80.3% (87.2%). With 2% as the upper limit of normal, no false positive results ensued. It is concluded that a two-step interpretation of the FATS (0.8% limit and 2% limit) may be regarded a valid qualitative index for steatorrhea. The FATS isotope ratio using single stools correlated well with FATS ratios in the 72-hr stool homogenates (r = 0.97). FATS therefore allows a convenient estimate of steatorrhea from measuring single stools. As a quantitative measure of fecal fat excretion, the FATS is unreliable.

Assessment of fat malabsorption

For the assessment of fat malabsorption, the standard method of measuring faecal fat excretion using a 5 day stool collection has been compared with the alternative methods: stool microscopy, a lipid tolerance test and a continuous marker technique for the estimation of fat content on a single stool sample. The lipid test, using an emulsion of arachis oil (Prosparol), was less reliable than had been expected with a sensitivity of 33% and a specificity of 45.4%. Stool microscopy using Oil Red O to stain fat globules had a sensitivity of 72.2% and a specificity of 95.4%. Fat estimation of a single stool sample using copper (1) thiocyanate showed a high correlation with that determined on a 5 day stool collection (p less than 0.001). It is concluded that lipid tolerance tests have little place in the estimation of fat absorption. In laboratories where faecal fats are not measured, microscopic examination of stool for fat globules provides a specific and relatively sensitive method for detecting steatorrhoea. The use of a continuous marker provides a method for assessing the degree of steatorrhoea on a single stool sample without the disadvantages of the conventional method of faecal fat analysis.

A study of fat absorption in cystic fibrosis patients and controls by a rapid micro procedure: a comparison with fecal fat excretion method

Fat absorption was studied in 11 Cystic Fibrosis patients and 6 controls by measuring a) fecal fat excretion and b) serum turbidity using a nephelometer between 0 and 2 hours after a butter-fat load. Cystic Fibrosis patients showed a mean +/- SEM fecal fat excretion of 21.6 +/- 5.5%, and controls a mean of 2.7 +/- 0.45%, of the dietary fat. The turbidity change expressed as delta turbidity showed a mean value of 1.37 +/- 0.57 in Cystic Fibrosis patients and 31.8 +/- 5.7 in controls. Fecal fat excretion method showed a good negative correlation with the butter fat method. The butter fat absorption method was also compared with fecal fat excretion in rats with induced malabsorption and control rats. The results obtained were comparable to those in the patients. The method described here is rapid and can be performed with small blood volumes and therefore may be suitable to study fat malabsorption in pediatric patients.

Serum isoamylase as a test for pancreatic insufficiency

Total and pancreatic serum isoamylases were performed on 38 control subjects (21 non-smokers and 17 smokers) and 21 consecutive patients with pancreatic insufficiency before and after meal stimulation. There was no difference in the fasting or stimulated levels of total amylase (T), pancreatic isoamylase (P), or % P/T between smokers and non-smokers. The P/T ratio was significantly reduced in patients with pancreatic insufficiency when compared with each of the control groups (p less than 0.0005). Eleven of 21 patients with pancreatic insufficiency had raised total serum amylase, but none had a rise in the pancreatic fraction or P/T ratio. Our findings indicate that the T, P, and P/T ratio of serum amylase are not influenced by smoking or meal stimulation. A reduced P/T ratio in a patient with steatorrhoea suggests pancreatic insufficiency as the cause. Hyperamylasaemia in patients with pancreatic insufficiency does not necessarily imply a relapse.

The value of [14C]phenyl acetic dipalmitate (PADP) as a test for maldigestion

[14C]phenyl acetic dipalmitate (PADP) was prepared and evaluated in vitro and in vivo. Upon incubation with lipase it was hydrolyzed into phenyl acetic acid and monoglycerides. Phenyl acetic acid is not metabolized by the body and is quantitatively excreted in urine. When tested in rats there was no tissue deposition of the 14C label in any of the organs studied. There was also no evidence of absorption from the colon. The newly prepared compound was evaluated in 15 human volunteers and 24 patients with chronic pancreatitis and compared to fecal fat and D-xylose. Normal volunteers had a urinary excretion of 34.5 +/- 6.4% of the administered 14C label in 5 h. Both fecal fat and PADP were abnormal in 16 of 20 patients with chronic pancreatitis. They were both normal in two, while in two other patients fecal fat was normal and PADP abnormal. Both of the latter patients had clinical evidence of steatorrhea but reduced oral intake due to pain. D-xylose was abnormal in five patients presumably due to bacterial overgrowth. Our findings indicate that PADP is a simple, accurate and rapid test for pancreatic function; is not dependent on fat intake and may be run concomitantly with D-xylose.