Table 5.
Sensitivity and specificity of individual assays and algorithms compared with both reference methods
|
Cytotoxigenic culture |
Cytotoxin assay |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| GDH EIA | Toxin*EIA 1 | Toxin EIA 2 | GDH EIA NAAT | Toxin EIA 2 NAAT | GDH toxin EIA 2 | GDH EIA | Toxin† EIA 1 | Toxin EIA 2 | GDH EIA NAAT | Toxin EIA 2 NAAT | GDH toxin EIA 2 | |
| Sensitivity (%; 95% CI) | 94·5% (92·9–95·8) | 45·6% (42·0–49·1) | 58·0% (55·0–61·1) | 91·5% (89·6–93·1) | 57·8% (54·8–60·9) | 57·0% (53·9–60·0) | 96·4% (94·8–97·7) | 66·9% (62·7–70·8) | 83·2% (80·3–85·8) | 95·6% (93·9–97·0) | 82·9% (80·0–85·6) | 81·8% (78·8–84·5) |
| Specificity (%; 95% CI) | 94·5% (94·1–94·9) | 99·2% (99·0–99·4) | 98·7% (98·4–98·9) | 98·0% (97·7–98·3) | 99·5% (99·3–99·6) | 99·4% (99·3–99·6) | 92·2% (91·7–92·7) | 99·3% (99·1–99·5) | 98·8% (98·6–99·0) | 95·9% (95·6–96·3) | 99·6% (99·4–99·7) | 99·5% (99·4–99·6) |
| PPV (%; 95% CI) | 61·0% (58·6–63·4) | 84·5% (80·7–87·8) | 80·0% (77·0–82·8) | 80·7% (78·3–82·9) | 90·7% (88·3–92·8) | 90·1% (87·5–92·2) | 43·9% (41·4–46·3) | 86·4% (82·8–89·6) | 81·2% (78·2–83·9) | 59·7% (56·8–62·5) | 92·1% (89·8–94·0) | 91·6% (89·2–93·6) |
| NPV (%; 95% CI) | 99·5% (99·3–99·6) | 95·2% (94·7–95·6) | 96·3% (95·9–96·6) | 99·2% (99·0–99·4) | 96·3% (95·9–96·6) | 96·2% (95·8–96·5) | 99·8% (99·6–99·8) | 97·9% (97·6–98·2) | 98·9% (98·7–99·1) | 99·7% (99·6–99·8) | 98·9% (98·7–99·1) | 98·9% (98·7–99·0) |
n=12 420, although small variations in n for each test or algorithm are shown in the appendix. GDH=glutamate dehydrogenase. EIA=enzyme immunoassay. NAAT=nucleic acid amplification test. PPV=positive predictive value. NPV=negative predictive value.
*
n=9191 because some centres continued to use the assay in the testing phase. Per-protocol version is in the appendix.
†
n=9160 because some centres continued to use the assay in the testing phase. Per-protocol version is in the appendix.