Table 5.
Diagnostic performance of presenting SUN (measured by dipstick) to detect any kidney disease, and a presenting EGFR of <60, <45, <30, and <15 mL/min/1.73
| Diagnosis criteria | Any kidney disease (AKI, AKD and CKD) | Presenting eGFR <60 mL/min/1.73 m2 | Presenting eGFR <45 mL/min/1.73 m2 | Presenting eGFR <30 mL/min/1.73 m2 | Presenting eGFR <15 mL/min/1.73 m2 |
| No of SUN tests in analysis | 655 | 649 | 649 | 649 | 649 |
| No of patients with diagnosis (%, prevalence) | 482 (73.6) | 368 (43.3) | 187 (28.8) | 115 (17.7) | 62 (9.6) |
| Area under ROC curve (95% CI) | 0.61 (0.56 to 0.65) | 0.67 (0.63 to 0.71) | 0.71 (0.67 to 0.76) | 0.78 (0.72 to 0.83) | 0.87 (0.81 to 0.93) |
| P value for area under ROC | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
| Optimal SUN threhold for diagnosis | Above testpad #1 | Above testpad #1 | Above testpad #1 | Above testpad #1 | Above testpad #1 |
| Younden's Index at this threshold | 21 | 33 | 38 | 51 | 64 |
| True positives | 143 | 121 | 100 | 76 | 51 |
| False negatives | 339 | 160 | 87 | 39 | 11 |
| False positives | 15 | 37 | 58 | 82 | 107 |
| True negatives | 158 | 331 | 404 | 452 | 480 |
| Sensitivity (%, 95% CI) | 29.7 (25.6 to 34.0) | 43.1 (37.2 to 49.1) | 53.5 (46.1 to 60.8) | 66.1 (56.7 to 74.7) | 82.3 (70.5 to 90.8) |
| Specificity (%, 95% CI) | 91.3 (86.1 to 95.1) | 90.0 (86.4 to 92.8) | 87.5 (84.1 to 90.3) | 84.6 (81.3 to 87.6) | 81.8 (78.4 to 84.8) |
| Positive likelihod ratio (95% CI) | 3.42 (2.07 to 5.66) | 4.28 (3.07 to 5.98) | 4.26 (3.23 to 5.61) | 4.3 (3.39 to 5.46) | 4.51 (3.67 to 5.55) |
| Negative likelihood ratio (95% CI) | 0.77 (0.72 to 0.83) | 0.63 (0.57 to 0.70) | 0.53 (0.45 to 0.62) | 0.4 (0.31 to 0.52) | 0.22 (0.13 to 0.37) |
| Positive predictive value (%, 95% CI) | 90.5 (85.2 to 94.0) | 76.6 (70.1 to 82.0) | 63.3 (56.7 to 69.4) | 48.1 (42.2 to 54.1) | 32.3 (27.9 to 37.0) |
| Negative predictive value (%, 95% CI) | 31.8 (30.2 to 33.4) | 67.4 (65.0 to 69.7) | 82.3 (79.9 to 84.5) | 92.1 (90.0 to 93.8) | 97.8 (96.2 to 98.7) |
| Test accuracy (%) | 46.0 (42.1 to 49.9) | 69.7 (66.0 to 73.2) | 77.7 (74.3 to 80.8) | 81.4 (78.1 to 84.3) | 81.8 (78.6 to 84.7) |
AKI, acute kidney injury; CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate; ROC, receiver operating characteristics; SUN, saliva urea nitrogen.