Lab Med Online.  2016 Jan;6(1):45-49. 10.3343/lmo.2016.6.1.45.

A Case of the False-negative D Phenotype in a Neonate with a Strongly Positive Direct Antiglobin Test Rest

• Jung YS
• Lim YA

• KMID: 2312292
• DOI: http://doi.org/10.3343/lmo.2016.6.1.45

Abstract

Accurate D antigen blood typing is needed owing to the clinical importance of the Rh blood group. We describe a female infant who was suspected to suffer from Rh incompatible hemolytic disease of the newborn, and who showed a strong positive direct antiglobin test (DAT) result and false red blood cell (RBC) agglutination in D typing. Using chloroquine dissociation of IgG, we confirmed that the antibodies coating her RBCs were of anti-D type. D typing with 0.8% RBC suspensions in saline using saline gel cards showed 2+ RBC agglutinations. After increasing the incubation time of dissociation by chloroquine for up to 4 hr, the dissociated RBCs began to show agglutination in both the tube technique (2+) and the gel card technique (4+) for D typing, although the DAT rest was still positive. Therefore, in order to prevent mistyping as a false-negative D blood group, whenever the D blood typing of a patient with a strong positive DAT rest does not show RBC agglutination, retesting of the D blood typing is recommended by using saline-suspended RBCs or dissociated RBCs.

Keyword

Hemolytic disease; Rh incompatibility; D blood typing; Direct antiglobin test; Chloroquine

MeSH Terms

Agglutination
Antibodies
Blood Grouping and Crossmatching
Chloroquine
Erythrocytes
Female
Humans
Immunoglobulin G
Infant
Infant, Newborn*
Phenotype*
Suspensions
Antibodies
Chloroquine
Immunoglobulin G
Suspensions

Figure

• 

  Fig. 1 Red blood cell (RBC) agglutination in the column agglutination test (CAT) for determining Rh(D) type. (A) CAT after 4 hr of chloroquine dissociation (4+). (B) CAT of RBC suspension in 0.8% normal saline before chloroquine dissociation (2+).

• 

  Fig. 2 Red blood cell agglutination in tube tests for determining Rh(D) type. (A) Tube test after 15 sec centrifugation (no agglutination). (B) Tube test after 45 sec centrifugation (trace). (C) Tube test after 4 hr of chloroquine dissociation (2+).

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