Table 3.
Dipstick scoresa to predict laboratory diagnosis of urinary tract infection using European guidelines.b
| Cut-off point (% at or above cut-off point) | Sensitivity | Specificity | PPV | NPV | Correctly classified % | LR+ve | LR−ve |
|---|---|---|---|---|---|---|---|
| ≥0 (100%) | 100 | 0 | – | – | 62 | 1 | – |
| ≥1 (83%), B | 93 | 34 | 70 | 73 | 70 | 1.40 | 0.22 |
| ≥1.5 (73%), L | 89 | 52 | 75 | 72 | 74 | 1.83 | 0.23 |
| ≥2 (59%), B+L, or N | 77 | 70 | 81 | 65 | 75 | 2.58 | 0.33 |
| ≥3 (19%), N+B | 28 | 96 | 92 | 45 | 54 | 7.17 | 0.75 |
| ≥3.5 (17%), N+L | 26 | 97 | 93 | 44 | 53 | 8.00 | 0.77 |
| ≥4.5 (12%), N+L+B | 18 | 98 | 94 | 42 | 48 | 9.09 | 0.84 |
| >4.5 (0%) | 0 | 100 | – | – | 38 | – | 1 |
a
Score weighted according to rounded logistic coefficients based on sum of nitrite = 2, leucocyte = 1.5, and blood = 1. Score was robust to weighting assumptions: there was similar performance for an unweighted score, or for a score weighted according to odds ratios.
b
103 colony-forming units per ml. PPV = positive predictive value. NPV = negative predictive value. LR+ve = likelihood ratio for a positive test. LR–ve = likelihood ratio for a negative test. B = blood. L = leucocyte. N = nitrate. UTI = urinary tract infection. Score gave an area under the ROC curve of 0.78 (95% CI = 0.74 to 0.83).