Table 2.
Comparison of the sensitivity and specificity based on CH4 cut-off when a baseline methane measurement (new test) is compared to the results of the full 10-sample lactulose breath test (reference test). United States of America (USA, results of this study) vs. Los Angeles (LA, Rezaie et al. [13])
| CH4 cut-off ≥ | Sensitivity (CI), % |
Specificity (CI) , % |
PPV (CI) , % |
NPV (CI) , % |
||||
|---|---|---|---|---|---|---|---|---|
| USA | LA | USA | LA | USA | LA | USA | LA | |
| 3 ppm | 95.2 (94.2–96.0) | 98.8 (98.2–99.3) | 92.9 (92.4–93.4) | 99.3 (99.1–99.4) | 77.6 (76.0–79.1) | 96.0 (95.1–96.9) | 98.7 (98.4–98.9) | 99.8 (99.7–99.9) |
| 4 ppm | 94.5 (93.5–95.4) | 97.3 (96.4–97.9) | 95.0 (94.6–95.5) | 99.6 (99.4–99.7) | 83.0 (81.5–84.4) | 97.7 (96.9–98.3) | 98.5 (98.3–98.8) | 99.5 (99.3–99.6) |
| 5 ppm | 93.1 (92.0–94.1) | 96.1 (95.1–96.9) | 96.6 (96.2–96.9) | 99.7 (99.6–99.8) | 87.5 (86.1–88.7) | 98.5 (97.8–99.0) | 98.2 (97.9–98.5) | 99.3 (99.1–99.4) |
| 6 ppm | 91.2 (90.0–92.3) | 94.6 (93.4–95.5) | 97.6 (97.2– 97.9) | 99.7 (99.6–99.8) | 90.6 (89.4–91.7) | 99.1 (98.5–99.5) | 97.7 (97.4–98.0) | 99.0 (98.8–99.2) |
| 7 ppm | 88.8 (87.4–90.0) | 93 (91.8–94.1) | 98.5 (98.2–98.7) | 99.9 (99.8–99.9) | 93.8 (92.7–94.7) | 99.3 (98.7–99.6) | 97.1 (96.8-97.5) | 98.7 (98.5–98.9) |
| 8 ppm | 86.2 (84.7–87.5) | 90.7 (89.3–92) | 99.2 (99.0–99.3) | 99.9 (99.9–100) | 96.4 (95.5–97.1) | 99.7 (99.2–99.9) | 96.5 (96.1–96.9) | 98.3 (98.1–98.6) |
| 9 ppm | 83.9 (82.4–85.4) | 88.8 (87.3–90.2) | 99.6 (99.5–99.7) | 100 (99.9–100) | 98.2 (97.6–98.2) | 99.9 (99.6–100) | 96.0 (95.6–96.4) | 98 (97.7–98.2) |
| 10 ppm | 81.0 (79.4–82.6) | 86.4 (84.8–87.9) | 100 | 100 | 100 (99.8–100) | 100 (99.8–100) | 95.3 (94.9–95.8) | 97.6 (97.3–97.8) |
The prevalence of methane positive subjects was 20.4% in the USA Sample (this study) and 15.5% in Los Angeles (Rezaie et al.).
CI = confidence interval; PPV = positive predictive value; NPV = negative predictive value.