A recent article by Beck et al[1] contributes to our understanding of hemolytic disease of the fetus and newborn (HDFN)
mediated by antibodies against non-Rhesus blood group antigen systems. However, there
are critical methodological and reporting errors that preclude the ability to draw
the conclusions asserted by the authors. First, the authors provide no compelling
evidence that the antibody causing the fetal anemia is due to anti-M other than a
positive indirect antiglobulin test (IAT) for anti-M in maternal plasma and a coincidentally
positive direct antiglobulin test (DAT) on neonatal cells. The authors provide no
information regarding plasma studies in the newborn, elution studies, low-incidence
antibody testing, or newborn M antigen typing. A positive newborn DAT is nondiagnostic
and requires further evaluation, as even a negative maternal IAT does not preclude
the possibility of HDFN to a low-incidence maternal alloantibody.[2] Further, contemporary and historical literature of larger case series found that
in HDFN caused by anti-M the neonatal DAT is more frequently negative than positive.[2]
[3]
[4] Therefore, the positive DAT cited by Beck et al could theoretically lower one's
suspicion for the cause of HDFN being solely due to anti-M. In addition, when discussing
any case of HDFN, but especially with anti-M where the antibody's isotype and reacting
temperature can be in question, the testing methods including platform technology,
temperature, and enhancement media are vital to the discussion.[5] Beck et al provide no information regarding the antibody identification or titer
techniques used in the maternal or neonatal testing nor do the authors provide methodological
description of the maternal breast milk testing. Though this case could be an important
addition to the growing body of evidence supporting anti-M as a cause of HDFN, further
investigation and reporting are required to definitively establish the conclusions
proclaimed by the authors.
