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APT Test, Stool

HbF, Fetal Hemoglobin, Alkali Denaturation Test

Test Codes

EPIC: LAB1231106, APT

Department

Toxicology

Instructions

The APT test is a qualitative procedure used to visually detect Fetal hemoglobin in a neonatal stool or gastric specimen. A specimen that does not show visual evidence of gross blood (pink-red) upon receipt by the Laboratory is inappropriate for analysis.

Specimen Collection Criteria

Collect: Random stool specimen or gastric contents in a sterile collection container.

• It is required that the specimen be red (grossly bloody) and not tarry.
• Transport specimen to the Laboratory immediately after collection.

Rejection Criteria

Specimens that are not red/grossly bloody.

In-Lab Processing

Do not store the specimen. Analyze immediately upon receipt in the Laboratory.

Storage

Specimen Stability for Testing:

Room Temperature (20–26°C or 68–78.8°F): 1 hour
Refrigerated (2–8°C or 36–46°F): 1 hour
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Specimens are disposed within 8 hours of testing.

Laboratory

Royal Oak Automated Chemistry Laboratory

Performed

Sunday – Saturday, 24 hours a day.
STAT results available within 2 hours of receipt in the Royal Oak Laboratory.
Routine results available within 24 hours.

Reference Range

Negative.

Test Methodology

Manual/Qualitative, Alkali Denaturation.

Interpretation

The test depends on the stability of fetal hemoglobin in the presence of alkali. Following addition of alkali and centrifugation, fetal hemoglobin will remain pink/red, whereas Hb A from maternal blood will be converted to alkaline hematin in 1-2 minutes and the solution will become yellow-brown.

Clinical Utility

The test is performed to determine whether fresh blood present in neonatal stool or gastric contents is of maternal or neonatal origin, however test sensitivity is poor (i.e., detection of small amounts of blood from a neonate is low). Red cells from a neonate will contain greater than or equal to 70% fetal hemoglobin, whereas maternal red cells normally contain less than 2% fetal hemoglobin.

CPT Codes

83033

Contacts

Last Updated

7/21/2024