Table 6.
Diagnostic test characteristics for serum samples from calves. Sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), accuracy, false positive (FP), and false negative (FN) for different Brix refractometer cut-points compared with 10 mg/mL of IgG as measured by ELISA.
| Cut Point Value | Se (%) | Sp (%) | Se + Sp 1 | PPV 2 (%) | NPV 3 (%) | Accuracy 4 (%) | FP 5 | FN 6 |
|---|---|---|---|---|---|---|---|---|
| 7.8% | 25.0 (11.0-46.1) | 100.0 (84.0-100.0) | 1.25 | 100.0 (84.0-100.0) | 88.0 (68.2-96.7) | 88.5 | 0 | 3 |
| 8.0% | 33.3 (17.0-54.4) | 100.0 (84.0-100.0) | 1.33 | 100.0 (84.0-100.0) | 92.0 (73.0-98.5) | 92.3 | 0 | 2 |
| 8.4% | 75.0 (53.9-89.0) | 100.0 (84.0-100.0) | 1.75 | 100.0 (84.0-100.0) | 95.7 (77.7-99.7) | 96.1 | 0 | 1 |
Se = sensitivity; Sp = specificity; 1 Sensitivity and specificity percentages converted into a unit value; 2 PPV = positive predictive value; 3 NPV = negative predictive value. 95% confidence interval shown in parentheses for Se, Sp, PPV, and NPV. 4 Accuracy = percentage of samples correctly classified as high (≥10 mg of IgG/mL) or low (<10 mg of IgG/mL). 5 FP = false positive; 6 FN = false negative.