The [¹⁴C]-triolein breath test is not valid as a test of fat absorption

Abstract

The [¹⁴C]-triolein breath test is used as a test of fat absorption. However, its validity has not been established. The aim of this study was to investigate, whether the absorption of [¹⁴C]-triolein could be estimated from the breath test, and whether the breath test could be useful as a clinical test. The [¹⁴C]-triolein absorption was estimated from faecal measurements, using ^5lCrCl₃ as nonabsorbable marker. The breath test was done according to the standard technique with hourly estimations of the ^l4C0₂ expiration. Fifty-one patients participated. A nearly perpendicular, curvilinear relation between the 6-h cumulative ¹⁴CO₂ expiration and the [¹⁴C]-triolein absorption was found, and no obvious cut-off level for normal ¹⁴CO₂ expiration could be identified. Accordingly, the diagnostic sensitivity of the breath test was 80% at the expense of a specificity of 45%. In 19 patients duplicate measurements were done. A high intra- and inter-individual variation in the fraction of absorbed [^l4C]-triolein, expired within 6 h, was found. It is concluded that expiration of ^l4CO₂ is influenced by factors other than the absorption of [^l4C]-triolein, and that the [^l4C]-triolein breath test is not useful as test of fat absorption.

Key Words:

• breath test
• carbon isotopes
• malabsorption