Fetal Hemoglobin Determination for Fetomaternal Hemorrhage

Also known as: FHGB

Clinical Use

Use

The Fetal Hemoglobin Determination test is designed to detect and quantify the extent of fetomaternal hemorrhage in pregnant or postpartum women. This is critical for assessing the need for Rh immunoglobulin (e.g., RhoGAM) in cases of suspected fetomaternal hemorrhage, which can occur during pregnancy or after childbirth. By determining the percentage of fetal red blood cells (RBCs) in the maternal circulation using flow cytometry, healthcare providers can accurately calculate the necessary dosage of RhIG and intervene appropriately to prevent hemolytic disease and other complications that may arise from fetal-maternal blood mixing.

Special Instructions

Not provided.

Limitations

The test is not suitable for males or nonpregnant females. Accurate calculation of RhIG dosage requires consideration of maternal height and weight, and users are advised to refer to the most recent AABB Technical Manual for guidance. Clotted or hemolyzed specimens are unacceptable, as are refrigerated specimens older than 120 hours (5 days) or ambient specimens older than 12 hours. Frozen specimens are also unacceptable, necessitating careful handling and timing of specimen transport and analysis.

Test Details

Methodology

Cell-based / Cytometry (Flow Cytometry)

Biomarkers

Fetal RBCs

Analyte

Percent Fetal RBCs

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Result Codes

55729-8 - Fetal RBC/RBC Bld FC-Rto

Result Turnaround Time

1-2 days

Specimen

Whole Blood

Volume

5 mL

Minimum Volume

0.5 mL

Container

Lavender (EDTA) or pink (K2EDTA)

Collection Instructions

Collect lavender (EDTA) or pink (K2EDTA). New York State Clients: Collect and ship Monday-Thursday only. Ship same day as collection.

Patient Preparation

Maternal, pregnant or postpartum whole blood.

Storage Instructions

Refrigerated.

Causes for Rejection

Clotted or hemolyzed specimens; refrigerated specimens greater than 120 hours old; ambient specimens greater than 12 hours old; specimens from males or nonpregnant females.