Utility of repeat testing in the evaluation for von Willebrand disease in pediatric patients.

BACKGROUND: Von Willebrand disease (VWD) is the most common inherited bleeding disorder and is caused by quantitative and qualitative defects in von Willebrand factor (VWF). The laboratory diagnosis of VWD in pediatric patients is complicated by VWF interassay and intra-assay variability, stress-induced elevations in VWF levels, and a lack of significant bleeding history with which to correlate test results.

OBJECTIVE: Guidelines recommend repeat testing in patients with a high suspicion of VWD and unclear laboratory assay results; however, no studies have evaluated the utility of repeat VWF testing in pediatric patients.

METHODS: This retrospective single-center cohort study aimed to determine clinical variables associated with requiring more than one test to diagnose VWD and to establish a cutoff VWF value above which further testing is not informative.

RESULTS: Of 811 patients evaluated for a suspected bleeding disorder, 22.2% were diagnosed with VWD, with ~70% diagnosed on the first test. Patients with VWD were younger (5.8 vs. 8.5 years, P = .002) and more likely to have a family history of VWD (38% vs. 22%, P < .001) than those without VWD. Univariate analysis failed to identify any clinical variables that correlated with needing multiple tests for a VWD diagnosis. A cutoff of 100 IU/dL for VWF antigen or activity on the first test yielded negative predictive values >95%.

CONCLUSIONS: We demonstrate that the majority of pediatric patients had diagnostic VWF values on the first set of testing. Pediatric patients without a family history of VWD and VWF levels >100 IU/dL may not need further testing to rule out the diagnosis of VWD.