Noninvasive Methods

Because small intestinal intubation for quantitative culture is inconvenient, expensive, and not widely available, a variety of surrogate tests for bacterial overgrowth in the small intestine have been devised based on the metabolic actions of enteric bacteria rather than on increases in the number of bacteria. Several indirect methods have been developed to overcome the problem of location-dependence of aspirates for culturing. A comparison between the small intestinal noninvasive tests versus invasive methods with culture of material obtained for diagnosis of SBBO is presented in Table 3. Most of these indirect tests lack sensitivity for reliable detection of SBBO. The main reason for this is the great variability of the microbiota and its metabolic profile. The tests are based on a specific bacterial metabolic activity. Thus, if this particular activity is not present in the microbiota of a SBBO patient, the test will yield a false-negative result. For this reason urinary excretion tests (e.g., indican excretion, D-xylose, conjugated para-aminobenzoic acid), and analysis of intestinal aspirates for bacterial metabolic products (e.g., deconjugated bile acids in serum) lack the required reliability for detection of SBBO, and have become obsolete (71-75). These tests will not be described further.

Table 3 Small Intestinal Noninvasive Tests Compared to Jejunal Culture (Gold Standard)


Sensitivity (%)

Specificity (%)


14C-D-xylose BT

Pregnancy And Childbirth

Pregnancy And Childbirth

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