Type 2M von Willebrand disease – more often misidentified than correctly identified

Abstract

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.

Evaluation of a new commercial von Willebrand factor multimer assay

“…Unfortunately, laboratory testing for VWD is imperfect, and all phenotypic tests are subject to error, as is multimer analysis. For example, a background error rate of~10% can be associated with phenotypic testing, although error rates for specific VWD types can be higher or lower [7,8]. 2M VWD in particular is more often misdiagnosed as Type 1 or 2A VWD than correctly diagnosed as 2M [6,8].…”

“…For example, a background error rate of~10% can be associated with phenotypic testing, although error rates for specific VWD types can be higher or lower [7,8]. 2M VWD in particular is more often misdiagnosed as Type 1 or 2A VWD than correctly diagnosed as 2M [6,8]. Most errors can be linked to analytical issues or postanalytical (mis)interpretation of test findings.…”

The elusive and heterogeneous pattern of type 2M von Willebrand disease: A diagnostic challenge

“…This condition is also seen in VWD patients lacking in large multimers, that is, in those with type 2A or type 3 or severe type 1, with VWF levels below 10 U/dL. 26,27 Since all the type 2M VWD patients described to date have had normal or only slightly reduced VWF levels, the combination of a defective or absent RIPA with normal or near normal VWF levels can point to both type 2M or type 2A…”

Comparison of an automated chemiluminescent assay to a manual ELISA assay for determination of von Willebrand Factor collagen binding activity on VWD plasma patients previously diagnosed through molecular analysis of VWF

“…This assay which is interpreted in a similar fashion, but remains under‐recognized, is not frequently used in routine practice as the ELISA (enzyme‐linked immunosorbent assay) method has not been fully automated. However, Favaloro et al identified that the 3 “standard” test panels (FVIII, VWF:Ag, VWF:RCo) must be optimized by VWF:CB assay to reduce misdiagnosis of VWD . In particular, diagnosis of type 2M VWD was missed by 75‐90% of laboratories using only 1 of the 2 VWF activity assays (VWF:RCo or VWF:CB), whereas the error rate was 3 times lower in the laboratories performing the 2 activity assays …”

“…However, Favaloro et al identified that the 3 "standard" test panels (FVIII, VWF:Ag, VWF:RCo) must be optimized by VWF:CB assay to reduce misdiagnosis of VWD. [8][9][10] In particular, diagnosis of type 2M VWD was missed by 75-90% of laboratories using only 1 of the 2 VWF activity assays (VWF:RCo or VWF:CB), whereas the error rate was 3 times lower in the laboratories performing the 2 activity assays. 8 Recently, a chemiluminescent method (HemosIL AcuStar VWF:CB; Instrumentation Laboratory, Bedford, MA, USA) has been commercialized.…”