Several diseases like pancreatic insufficiency or hepatic disorders cause malabsorption or maldigestion. The resulting changes in stool composition (e.g., in moisture, nitrogen content, or fat content) provide important information for medical diagnostics.

Time-consuming lab methods which require a significant amount of sample preparation can be replaced by near-infrared spectroscopy (NIRS) for fast screening of human stool samples with no sample preparation. The NIRS method is easy to use – no chemicals are required and results are given for several parameters within one minute.

DS2500 Solid Analyzer with human stool samples.
Figure 1. DS2500 Solid Analyzer with human stool samples.

522 human stool samples were analyzed on a Metrohm DS2500 Solid Analyzer with a modified DS2500 Holder for petri dishes (Figure 1). Stool samples were positioned into the petri dishes for the analysis in diffuse reflection mode. Reference values for moisture, fat, and nitrogen content were obtained with the respective primary methods. 

Equipment Metrohm number
DS2500 Solid Analyzer 2.922.0010
DS2500 Holder 6.7430.040
Vision Air 2.0 Complete 6.6072.208

The obtained Vis-NIR spectra (Figure 2) were used to create prediction models for the different reference parameters. The data set was split into calibration and validation sets to verify the quality of the prediction models. Correlation diagrams which display the relation between the Vis-NIR prediction and the reference values are shown in Figures 3–5 together with the respective figures of merit (FOM).

Figure 2. Selection of Vis-NIR spectra of human stool samples. Data was obtained with a DS2500 Solid Analyzer.
Figure 3. Correlation diagram and the respective FOMs for the prediction of moisture content in human stool using a DS2500 Solid Analyzer.
Figure 4. Correlation diagram and the respective FOMs for the prediction of fat content in human stool using a DS2500 Solid Analyzer.
Figure 5. Correlation diagram and the respective FOMs for the prediction of nitrogen content in human stool using a DS2500 Solid Analyzer.

This Application Note shows the feasibility of NIR spectroscopy for the analysis of moisture, fat, and nitrogen content in human stool samples by NIRS, which can be conducted without chemicals or sample preparation.

Contact

Metrohm AG

Ionenstrasse
9100 Herisau

Contact