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Type 2M von Willebrand disease – more often misidentified than correctly identified
Author(s) -
Favaloro E. J.,
Bonar R. A.,
Mohammed S.,
Arbelaez A.,
Niemann J.,
Freney R.,
Meiring M.,
Sioufi J.,
Marsden K.
Publication year - 2016
Publication title -
haemophilia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.213
H-Index - 92
eISSN - 1365-2516
pISSN - 1351-8216
DOI - 10.1111/hae.12903
Subject(s) - von willebrand disease , von willebrand factor , medicine , pediatrics , platelet
Appropriate diagnosis of von Willebrand disease ( VWD ), including differential identification of qualitative vs. quantitative von Willebrand factor ( VWF ) defects has important management implications, but remains problematic. Aim The aim of the study was to assess whether 2M VWD , defining qualitative defects not associated with loss of high molecular weight ( HMW ) VWF , is often misidentified, given highly variable reported frequency ranging from 0 to ~60% of all type 2 VWD . Methods A comparative evaluation of laboratory ability to appropriately identify 2M VWD ( n = 4) vs. HMW VWF reduction ( n = 4), as sent to participants of an international external quality assessment programme. Results Laboratories had considerably greater difficulty identifying type 2M VWD , correctly identifying these on average only 29.4% of occasions, with the 70.6% error rate representing use of insufficient test panels (41.7%), misinterpretation of test results (10.0%) and analytical errors (13.3%). One type 2M case, giving a median of 49 U dL −1 VWF :Ag, was more often misidentified as type 2A/2B VWD (46.7%) than 2M (34.8%). Another 2M case, giving a median of 189 U dL −1 VWF :Ag, was instead often misidentified as being normal (non‐ VWD ) (36.4%), with identifications of type 2A/2B VWD (13.6%) also represented. In comparison, errors in identification of HMW VWF reduced samples only averaged 11.5%, primarily driven by use of insufficient test panels (6.3%) or misinterpretation of results (4.2%) and infrequently analytical errors (1.0%). Conclusion Type 2M VWD is more often misidentified (70.6%) than correctly identified as 2M VWD (29.4%), and potentially explaining the relative under‐reported incidence of 2M VWD in the literature.