GRADE test accuracy evidence summary for using a platelet-dependent VWF activity assay/VWF:Ag ratio < 0.7 to diagnose type 1 VWD
| Outcome . | Studies/ patients, n . | Study design . | Factors that may decrease CoE . | Effect per 1000 patients tested; pretest probability of 30% . | Test accuracy CoE . | ||||
|---|---|---|---|---|---|---|---|---|---|
| Risk of bias . | Indirectness . | Inconsistency . | Imprecision . | Publication bias . | |||||
| True positives* | 5/204 | Cohort and case-control type studies | Serious† | Not serious | Not serious | Not serious | None | 278 (260-295) | ⨁⨁⨁◯ Moderate |
| False negatives‡ | 22 (5-40) | ||||||||
| True negatives§ | 4/994 | Cohort and case-control type studies | Serious† | Not serious | Serious¶ | Seriousǁ | None | 573 (441-700) | ⨁◯◯◯ Very low |
| False positives# | 127 (0-259) | ||||||||
| Outcome . | Studies/ patients, n . | Study design . | Factors that may decrease CoE . | Effect per 1000 patients tested; pretest probability of 30% . | Test accuracy CoE . | ||||
|---|---|---|---|---|---|---|---|---|---|
| Risk of bias . | Indirectness . | Inconsistency . | Imprecision . | Publication bias . | |||||
| True positives* | 5/204 | Cohort and case-control type studies | Serious† | Not serious | Not serious | Not serious | None | 278 (260-295) | ⨁⨁⨁◯ Moderate |
| False negatives‡ | 22 (5-40) | ||||||||
| True negatives§ | 4/994 | Cohort and case-control type studies | Serious† | Not serious | Serious¶ | Seriousǁ | None | 573 (441-700) | ⨁◯◯◯ Very low |
| False positives# | 127 (0-259) | ||||||||
Sensitivity, 0.93 (95% CI, 0.83-0.94); specificity, 0.82 (95% CI, 0.63-0.99). Pooled in proportion; not enough studies to pool as test accuracy results.
CoE, certainty of the evidence.
Patients with type 2 VWD.
All included studies were judged to be low risk of bias for test. Although there was unclear reporting about when the index test was conducted in some studies, the certainty of evidence was generally not downgraded for risk of bias. The patient selection risk of bias was high because of the case control design and reference standard interpretation leading to serious risk of bias.
Patients incorrectly classified as not having type 2 VWD.
Patients without type 2 VWD.
Considering the upper vs the lower boundary of the effect estimate may lead to a different clinical decision.
Prevalences are 30%. This is typically seen in patients investigated for type 2 VWD because of a low VWF:RCo/antigen ratio.
Patients incorrectly classified as having type 2 VWD.