Utility of the platelet function analyser (PFA-100/200) for exclusion or detection of von Willebrand disease: A study 22 years in the making

INTRODUCTION: von Willebrand disease (VWD) is the most common inherited bleeding disorder and may alternatively arise as an acquired condition (AVWS). These represent deficiency and/or defects in von Willebrand factor (VWF). Closure times (CTs) obtained from the platelet function analyser (PFA) are highly sensitive to both VWD/AVWS. The current study has evaluated the utility of the PFA-100/-200 to exclude or detect laboratory identified VWD.

MATERIALS AND METHODS: An evaluation of the success or otherwise of prospective PFA testing to help exclude or detect VWD using data from a locally maintained database. This database contains patient information, results of PFA testing, results of VWF testing, platelet count and hematocrit, and additional information, for a current total of 3678 entries representing over 2 decades of testing.

RESULTS: According to selection criteria, a total of 142 samples were identified as derived from patients with VWD. All but one of these were also identified to have abnormal PFA CTs. Additional data sets of patients with 'low VWF' (n = 137), or borderline normal VWF (n = 163) were also identified, as well as patients with thrombocytopenia and/or low hematocrit (n = 487). In these cohorts, PFA CTs were often (but not always) abnormal. There was a strong association between VWF test parameter values and PFA CTs. Additional study samples comprised cases with normal VWF parameters but prolonged CTs (n = 594), as well as cases with normal VWF and normal CTs (n = 1292), permitting calculation of sensitivity of abnormal PFA for VWD (99.3%), as well as specificity (68.5%), negative predictive value (99.9%) and positive predictive value (19.2%), for a prevalence of 7.0%. Comparatively, normal PFA CTs were better able to exclude VWD than normal test results for individual VWF parameters.

CONCLUSION: This study reports on an evaluation of PFA CTs for identification or exclusion of VWD. In our dataset, representing over 22 years of experience, normal PFA CTs were able to predict absence of VWD with higher sensitivity than individual VWF test results.