TABLE 2

Laboratory Evaluation for HS in a Jaundiced Neonate

HS Ratio (MCHC/MCV)EMA FlowaIncubated Osmotic FragilityDNA Sequencingb
Neonates with HS will generally have a high MCHC and a low MCV, producing an elevated ratio (>0.36)EMA dye binds stoichiometrically to band 3 and Rh-related membrane proteins. Decreased fluorescence intensity of EMA-tagged erythrocytes due to loss of membrane proteins is seen in HS. Decreased EMA binding is also seen in other disorders such as hereditary pyropoikilocytosis and congenital dyserythropoietic anemia IIHS erythrocytes are more susceptible to osmotic lysis than normal erythrocytes due to decreased membrane surface area. Incubation overnight stresses the already fragile HS erythrocyte, accentuating the defect. Spherocytes from any cause, including ABO incompatibility, will yield a positive result on osmotic fragility testingNot needed to diagnosis most cases of HS. However, it can establish the diagnosis in difficult cases. Consider sequencing of relevant genes when family history is negative and severe DAT-negative hemolysis is idiopathic
  • a Available in many reference laboratories.

  • b Available in selected hematology/genetics reference laboratories. For example: Blood Disease Reference Hematology Laboratory, http://www.yaleblooddiseaselab.org/, 310 Cedar Street, CB 541a, New Haven, CT 06520, Tel. (203)737-1349, Fax (203)785-3896; ARUP Laboratories, http://www.aruplab.com/testing, 500 Chipeta Way, Salt Lake City, UT 84108, Tel. (800)522-2787, Fax (800)522-2706; GeneDx, http://www.genedx.com, 207 Perry Parkway Gaithersburg, MD 20877, Tel. (301)519-2100, Fax (301)519-2892; and Mayo Medical Laboratories, http://www.mayomedicallaboratories.com/, 3050 Superior Drive NW, Rochester, MN 55901, Tel. (800)553-1710, Fax (507)284-1759.