Table 2.
Types of Comparisons Using Likelihood Ratios
| Finding | Positive LR | Negative LR |
|---|---|---|
| Compare the accuracy of different diagnostic tests for the same diagnosis | ||
| Physical findings, detecting ascites3,4 | ||
| Bulging flanks | 2.0 | 0.3 |
| Flank dullness | 2.0 | 0.3 |
| Edema | 3.8 | 0.2 |
| Fluid wave | 6.0 | 0.4 |
| Shifting dullness | 2.7 | 0.3 |
| Compare the diagnostic impact of a test's positive result to its negative result | ||
| Hyperresonance, detecting chronic airflow obstruction5 | 5.1 | NS |
| Pleuritic component to chest pain, detecting myocardial Infarction6 | 0.2 | 1.3 |
| Compare the accuracy of the same test for different definitions of disease | ||
| Late-peaking systolic murmur7 | ||
| Detecting severe aortic stenosis | 3.0 | 0.2 |
| Detecting moderate-to-severe aortic stenosis | 24.2 | 0.3 |
| Compare the accuracy of different levels of the same test for the same diagnosis | ||
| CAGE questions, detecting alcohol abuse and dependence8 | ||
| 0 positive | 0.1 | — |
| 1 positive | NS | — |
| 2 positive | 4.5 | — |
| 3 positive | 13.3 | — |
| 4 positive | 101 | — |
| 1 or more points | 4.7 | 0.1 |
| Compare the accuracy of the same test for the same diagnosis, in different clinical settings | ||
| Tachypnea, detecting pneumonia in children9 | ||
| All children | 2.2 | 0.4 |
| Disease duration <3 days | NS | NS |
| Disease duration 3 to 5 days | NS | NS |
| Disease duration ≥6 days | 3.5 | 0.1 |
Diagnostic standards: for ascites, peritoneal fluid by ultrasonography; for chronic airflow obstruction, FEV1/FEV <0.6; for myocardial infarction, cardiac enzymes or ECG, or both; for moderate and severe aortic stenosis, peak aortic flow velocity 2.6–3.5 m/s and ≥3.6 m/s, respectively; for alcohol abuse and dependence, DSM-III criteria; for pneumonia, infiltrate by chest radiograph.
Definition of findings: CAGE indicates 4 questions: have you Cut down on drinking?, have you been Annoyed by criticism?, are you Guilty about drinking?, have you ever had Eye-opener drinks?; tachypnea indicates a respiratory rate >60 breaths per minute in children <2 months old, >50 breaths per minute in children 2–12 months old, and >40 breaths per minute in children ≥1 year old.
NS, not significant, i.e., the LR's 95% confidence interval includes the value of 1.0. For the other LRs in the Table, the confidence intervals have been omitted for clarity although they all exclude the value of 1.0.