Latex Agglutination Test for Differentiating Neonatal Blood from the Maternal Blood in the Meconium

Park, Ile Kyu; Kim, Duck An; Lee, Woong Soo; Kim, Think You; Kim, Chang Ryul

Abstract

BACKGROUND: The Apt test is used for differentiating neonatal blood from the maternal blood in the meconium. The test requires a sufficient amount of blood to be detectable to the naked eyes. But many of the specimens in the hospital laboratory contain only a small amount of blood and is not detectable to the naked eyes and usually the results are reported 'impossible to determine' due to the small amount of blood. We developed a latex agglutination test to solve this problem and to differentiate the neonatal blood from the maternal blood in a small amount that was not detectable with the naked eyes.
METHODS
Latex reagents for hemoglobin A (Hb A) and hemoglobin F (Hb F) were made. Ten milligrams of meconium were dissolved in 1mL of deionized water (DW). Ten milligrams of meconium that had shown negative results for both of the above reagents were mixed, each with 10microL of whole blood (WB) from 10 pregnant women and 10 neonates who had various hemoglobin concentrations (10-17 g/dL). Each of the 20 mixtures was dissolved in 1 mL of DW (WB 10microL/mL). Then, serial dilutions were made at a ratio of 1:10 until the final concentration of 10 pL/mL. Each of the six dilutes were tested with the two latex reagents.
RESULTS
The dilutes of WB 10microL/mL looked red, WB 1microL/mL looked pink and all other dilutes showed no colors to the naked eyes. The reagent for Hb A showed agglutination in dilutes from WB 1microL to 1 nL/mL DW from all of the 20 persons. The reagent for Hb F reacted with dilutes from WB 1microL to 1 nL/mL DW from the ten neonates but did not react with those from any pregnant women.
CONCLUSIONS
The latex agglutination test can be applied to the specimen with no color detectable to the naked eyes after dilution. The specimen reacted with both the Hb A and Hb F reagents could be determined as fetal blood and the one that reacted with the reagent only for Hb A could be determined as maternal blood.