Table 3.
Results of group A vs group B analyses: sensitivity and specificity of the different questions, clinical features and laboratory features included in the anamnestic, clinical and laboratory item, respectively
| Sensitivity (%) | 95% CI (%) | Specificity (%) | 95% CI (%) | |
|---|---|---|---|---|
| Questionnaire item | ||||
| 1 →1 Do you remember one or more episodes of small red spots on your skin particularly involving the lower limbs? | 83.5 | 79.0 to 87.9 | 89.9 | 85.6 to 93.8 |
| 4 → 2 Have you ever had red spots on your lower extremities which leave a brownish colour after their disappearance? | 74.3 | 69.0 to 79.5 | 94.7 | 91.8 to 97.6 |
| 17 → 3 Has a doctor ever told you that you have viral hepatitis? | 83.1 | 78.6 to 87.6 | 38.6 | 32.2 to 44.9 |
| Clinical item | ||||
| Constitutional symptoms | 81.5 | 76.9 to 86.2 | 56.8 | 50.3 to 63.3 |
| Articular involvement | 63.0 | 57.2 to 68.7 | 57.0 | 50.6 to 63.5 |
| Vascular involvement | 87.9 | 84.0 to 91.8 | 78.5 | 73.1 to 83.9 |
| Neurological involvement | 64.4 | 58.6 to 70.2 | 86.5 | 81.8 to 91.2 |
| Laboratory item | ||||
| Low serum C4 | 69.6 | 64.0 to 75.2 | 74.5 | 68.3 to 80.6 |
| Rheumatoid factor (RF) positivity | 85.8 | 81.5 to 90.1 | 53.7 | 46.8 to 60.7 |
| Presence of serum M component | 83.1 | 78.4 to 87.8 | 72.8 | 66.2 to 79.3 |
| Group A vs group B | ||||
| ‘At least 2 out of the 3 questions’ | 83.8 | 79.4 to 88.2 | 93.8 | 90.7 to 97.0 |
| ‘At least 3 out of the 4 features’ among constitutional symptoms, articular, vascular or neurological involvement | 70.2 | 64.7 to 75.8 | 84.5 | 79.5 to 89.4 |
| ‘At least 2 out of the 3 features’ among serum C4 levels, RFs and serum M component | 84.2 | 79.4 to 89.0 | 79.6 | 73.4 to 85.9 |