GRADE test accuracy evidence summary for using a platelet-dependent VWF activity assay/VWF:Ag ratio < 0.5 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* | 3/95 | Cohort and case-control type | Serious† | Not serious | Not serious | Serious‡ | None | 174-237 | ⨁⨁◯◯ Low |
| False negatives§ | 63-126 | ||||||||
| True negatives¶ | 0/0 | 693-700 | — | ||||||
| False positivesǁ | 0-7 | ||||||||
| 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* | 3/95 | Cohort and case-control type | Serious† | Not serious | Not serious | Serious‡ | None | 174-237 | ⨁⨁◯◯ Low |
| False negatives§ | 63-126 | ||||||||
| True negatives¶ | 0/0 | 693-700 | — | ||||||
| False positivesǁ | 0-7 | ||||||||
Sensitivity, 0.58-0.79; specificity 0.99-1.00. Specificity assumed to be 100% with a ratio cutoff < 0.5.
Prevalences are 30%; typically seen in patients investigated for VWD because of a personal history of abnormal laboratory test (eg, increased partial thromboplastin time).
CoE, certainty of the evidence.
Patients with type 2 VWD.
Serious patient selection risk of bias due to case-control design. Also, issues around labeling as type 2M were noted.
Small number of subjects.
Patients incorrectly classified as not having type 2 VWD.
Patients without type 2 VWD.
Patients incorrectly classified as having type 2 VWD.