Laboratory diagnosis of von Willebrand disorder - Current practice in the Southern Hemisphere

A survey of 44 laboratories was conducted to evaluate current testing proficiency in the diagnosis of von Willebrand disorder (nuWD) and to assess recent changes in test practices. Laboratories performed their usual panel of tests for nuWD and interpreted results for the likelihood of nuWD and potential subtype. Samples were as follows: normal plasma; borderline normal or abnormal levels of von Willebrand factor (nuWF) and factor VIII; type 3 nuWD; type 2A nuWD; and 2 samples from a healthy person, processed after handling at 22degreesC and 4degreesC, respectively. Interassay and within-method coefficients of variation were similar for all assays (approximately 15%-25%). Most laboratories reported test values consistent with expected findings and made correct interpretations, although discrepant results for 5% to 10% of responses are of concern. For the sample stored at 4degreesC, all laboratories detected low or borderline levels of nuWF and factor VIII coagulant, and no laboratory identified this sample as from a healthy person. In contrast, for the sample stored at 22degreesC, most laboratories reported normal results. Compared with previous results, performance of some assays has declined while that of others has increased. Laboratories generally are proficient in tests for nuWD, and transport of samples at 4degreesC before processing may lead to false identification of nuWD, suggesting that NCCLS guidelines should be reviewed.