Near infrared reflectance measurement of nitrogen faecal losses

Energy intake, metabolic balance and growth in preterm infants fed formulas with different nonprotein energy supplements

OBJECTIVE

To study metabolic and energy balances, growth and composition of increased body mass in healthy preterm infants fed control formula or control formula with three different nonprotein energy supplements.

PATIENTS AND METHODS

Growing preterm infants (birth weight < 1,500 g and gestational age < 31 weeks) were fed standard preterm formula (control group) or the same formula enriched with three different nonprotein energy supplements. An energy supplement of 23 kcal/kg/day was achieved by adding medium-chain triglyceride and dextrinomaltose in three different caloric ratios: 33:66 in group A, 66:33 in group B, and 85:15 in group C. Energy balance was determined by open-circuit continuous (5-6 hours) measurements of energy expenditure, with simultaneous measurement of 24-hour urinary nitrogen excretion. Metabolic balance was determined by measurements of energy intake, energy oxidation, and energy output in urine and stool. The composition of body mass accretion was determined as the accretion of fat and protein in the total weight gain.

RESULTS

The fat accretion (4.9, 5.9, 6.2, and 3.8 g/kg/day in groups A, B, C and D, respectively) correlated directly with fat intake. Infants receiving standard energy intake had a fat percentage of weight gain significantly lower (28%) than that of the high-energy intake groups (31%, 40%, and 38% in groups A, B, and C, respectively). This difference corresponded to the results obtained from skinfold thickness measurements.

CONCLUSIONS

Excess nonprotein energy is stored as fat regardless of its source (fat or carbohydrate). High caloric and medium-chain triglyceride intake in otherwise healthy growing preterm infants does not promote nitrogen retention.

Water, fat, nitrogen, and sugar content in feces: reference intervals in children

Malabsorption-maldigestion syndromes are commonly found in several gastrointestinal diseases. Quantitative measures of fecal nutrients are important tools for the detection and diagnosis of these syndromes. Adequate food intake is important in the nutrition of children, especially during the first year of life. We have analyzed 180 stools of healthy children, divided into four age groups, to obtain the reference intervals of the major nutrients such as water, fat, nitrogen, sugar, and starch. Quantification of the nutrients was done by means of a near-infrared analyzer (Fenir 8820). Results show that this instrument exhibits a low coefficient of variation for all the nutrients except for starch. Fecal water, fat, nitrogen, and sugar concentrations ranged from 68.7 to 96.1 g/100 g, 0 to 14.5 g/100 g, 1.3 to 2.3 g/100 g, and 0.7 to 3.8 g/100 g, respectively. The results for the starch analyses were not acceptable because of instrument limitations. Near-infrared reflectance spectroscopy appears to be an alternative to standard chemical methods.

Determination of fecal fat concentration by near infrared spectrometry for the screening of pancreatic steatorrhea

CONCLUSIONS

Near infrared reflectance analysis (NIRA) is a useful test for diagnosing fat malabsorption. Three-day stool collection and determination of fecal fat output are recommended. The measurement of fat concentration on spot samples may be of some use only in screening malabsorption of pancreatic origin; moreover, it does not discriminate between steatorrhea resulting from pancreatic insufficiency and that caused by gastrointestinal disorders.

BACKGROUND

NIRA has been proposed as an accurate method for the determination of fecal fat excretion. The aim of this study was to ascertain whether utilization of this technique to measure fat concentration in spot samples of feces is useful in screening for malabsorption.

METHODS

Twenty-five patients with chronic pancreatic disease and 95 with other digestive disorders were studied. In all patients, fecal fat assay with NIRA was performed on three different samples from each daily stool collection for 3 d. In 14 patients with pancreatic disease and 21 with gastrointestinal disorders, a colorimetric assay for fecal fat was performed for comparison.

RESULTS

When mean 3-d or daily fat fecal output were considered, a strict linear relationship was found between NIRA and the colorimetric method (r = 0.97 and 0.94, respectively). Using fat concentration, the two tests correlated less well (r= 0.74). Fat concentration was significantly higher in pancreatic than in nonpancreatic steatorrhea, even though values overlapped widely, and thus discrimination was not possible. The diagnostic efficiency of fat concentration for pancreatic and nonpancreatic steatorrhea was 72 and 61%, respectively.

Simultaneous determination of fecal fat, nitrogen, and water by near-infrared reflectance spectroscopy

BACKGROUND

Determinations of fecal fat and nitrogen reveal evidence of malabsorption and assist in estimating the efficacy of pancreatic enzyme treatment. Seventy-two-hour stool collection, with chemical analysis of fecal fat, and Kjeldahl's method for measurement of fecal nitrogen are generally accepted as standard methods for making these determinations. However, these traditional methods are expensive, time-consuming, and cumbersome. This study evaluated the efficiency and validity of an alternative method, using near-infrared reflectance spectroscopy (NIRS) and compared results with those of the standard methods.

METHODS

Near-infrared reflectance spectroscopy is a secondary method: The instrument first has to be calibrated with samples analyzed by the standard method. Sixty-three stool samples with known fat content (range 4.79-292.5 mg/g), 24 samples with known nitrogen content (range 5.36-19.38 mg/g), and 24 samples with known water concentration (range 60.1-82.22%) served for calibration. A further 69 samples were analyzed to validate the procedure.

RESULTS

There was a satisfactory correlation between the measurements produced by near-infrared reflectance spectroscopy and those produced by standard methods: fat r = 0.97; nitrogen r = 0.94; water r = 0.96.

CONCLUSIONS

Near-infrared reflectance spectroscopy appears to be a reliable, simple, and rapid method of measuring different fecal components-as precise and accurate as the standard methods. Stool samples should be analyzed immediately after collecting or stored only a few days before analyzing.

Infrared analysis in clinical chemistry: its use in the laboratory and in non-invasive near patient testing

Laboratory based NIR analysers have been available for some time. The recent development of more portable equipment such as the commercially available Futrex-9000 NIR transmittance blood chemistry analyser, which can be used to analyse relatively opaque samples for a mixture of components, shows promise but requires further evaluation for routine clinical use. NIR equipment for general use has only recently become available and is therefore relatively expensive. However, as the development of new applications occurs the instrumentation will become more widely used, which will inevitably result in reduced capital cost. The advantages of NIR systems are speed, portability, lack of consumables, dry chemistry, non-invasive, modest running costs, virtually no moving parts and almost infinite applications in clinical biochemical analysis. It is likely that the first applications of NIR will be where there is a requirement for multiple assays such as glucose, urea and bilirubin and where sample size is a limitation. Thus non-invasive near patient testing may become common in the future in settings such as neonatal units, renal units, diabetic clinics and intensive care units.

Fecal fat measurement in the presence of long- and medium-chain triglycerides and fatty acids. Comparison of three methods

BACKGROUND

It has been suggested that some of the limitations of the Van de Kamer method for fecal fat measurement could be overcome with the Jeejeebhoy method or the near-infrared reflectance assay.

METHODS

To test this hypothesis, a fecal fat test was carried out with the three methods, adding butter or MCT oil to the diet of four steatorrhoic patients. An in vitro recovery study of long- and medium-chain triglycerides was also performed.

RESULTS

The Jeejeebhoy method measured long- and medium-chain fats more accurately than the Van de Kamer method. It found consistently higher steatorrhea values. Mean results of the near-infrared reflectance analysis resembled those of the Van de Kamer method, but with wide discordance of individual data.

CONCLUSION

The Jeejeebhoy method is more accurate than the Van de Kamer method for fecal fat measurement. The difference may be clinically relevant when most fecal fatty acids derive from medium-chain triglycerides. Near-infrared reflectance may be a viable proposition only when a greater degree of approximation is acceptable.

Pancreatic extracts are necessary for the absorption of elemental and polymeric enteral diets in severe pancreatic insufficiency

Tube feeding nutrition, either elemental or polymeric, is increasingly used in patients with digestive problems. Pancreatic insufficiency is a widely accepted indication for the use of an elemental formula, which requires less residual digestive capacity. To confirm this assumption, we have compared the absorption of elemental and polymeric diets and the effect of exogenous pancreatic enzymes in a patient on long-term total enteral feeding after total pancreatectomy. Malabsorption of both formulas was observed without enzyme supplementation. A marked improvement of fat and nitrogen absorption was obtained when pancreatic enzymes were added to both enteral diets. It is concluded that pancreatic enzymes should always be added to liquid diets in pancreatic insufficiency. No clear advantage is to be anticipated by the use of elemental as compared with polymeric diets.