(1211) Breathing new life into gestational diabetes diagnosis: pilot study of a novel non-invasive breath test

To evaluate the feasibility and diagnostic accuracy of exogenous glucose oxidation, as measured by an oral ¹³C‑glucose breath test for diagnosing gestational diabetes mellitus (GDM).

Study Design:

This single center prospective pilot study included individuals with singleton pregnancies scheduled for a 100-gram oral glucose tolerance test (OGTT) before 33 weeks’ gestation. Participants ingested 100g ¹³C-labelled glucose after an overnight fast. Venous glucose was obtained before ingestion and 1, 2, and 3 hours after. GDM was diagnosed with ≥2 abnormal values. Breath samples were collected every 15 minutes for 3 hours and analyzed by GC-isotope‑ratio mass spectrometry. Percent dose recovered (PDR) was calculated from the breath enrichment of ¹³CO₂ multiplied by assumed CO₂ production rates, so that the fraction of oxidized ¹³C-glucose (tracer) represented the fraction of the ingested glucose (tracee) metabolized to CO₂. Feasibility outcomes were recruitment and test completion. Diagnostic accuracy was assessed using the area under the receiver operating characteristic (ROC) curve (AUC). Pearson correlation coefficient was used to calculate the agreement between glycemia and exogenous glucose oxidation. The study protocol was approved by the institutional review board committee.

Results:

All 20 participants completed 3 hours of breath-test sampling; no adverse events occurred. Patients diagnosed with GDM (n=3) had a lower, yet not reaching significance, median PDR at 3 hours (PDR3h) than in those without GDM [9.4 (7.5-10.3) vs 10.6 (9.6-13.5)]. PDR3h discriminated GDM with an AUC 0.75 (95 % CI 0.33-1.00), (Figure 1). A threshold of PDR3h < 9.4% yielded 67% sensitivity and 82% specificity. PDR3h correlated inversely with OGTT glucose AUC (r = -0.48, r² = 0.23, p = 0.03), (Figure 2).

Conclusion:

The ¹³C‑glucose breath test was readily completed and allowed quantification of ingested glucose metabolism. PDR3h showed a moderate ability to identify GDM and was inversely correlated with OGTT. These findings support exploring this novel non-invasive diagnostic approach in larger cohorts.