Lab Dept:


Test Name:


General Information

Lab Order Codes:



Alpha-1-Antitrypsin Clearance; A1A Clearance; AAT Clearance

CPT Codes:

82103 – Alpha-1-antitrypsin; total

Test Includes:

Clearance result in mL/24 h, stool A1A concentration in mg/dL and serum A1A concentration in mg/dL.


Test Indications:

Useful for diagnosing protein losing enteropathies.

Lab Testing Sections:

Chemistry - Sendouts

Referred to:

Mayo Medical Laboratories (MML Test: 8835/CA1A)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

1 - 2 days, test set up Monday - Saturday

Special Instructions:

Both feces and serum are required for this test. The blood must be drawn during the stool collection period.


Specimen Type:

Blood and stool (24 hour collection)


Blood: Red top tube

Stool: Stool containers supplied by Mayo Medical Laboratories (Supply T291) and obtained from Children’s laboratory

Draw Volume:

3 mL (Minimum: 1.5 mL) blood

Entire 24 hour collection of stool, frozen

Processed Volume:

1 mL (Minimum: 0.5 mL) serum

Entire 24 hour collection of stool, frozen


Blood: Must be drawn during the stool collection period.

Stool: Each stool obtained during the collection can be sent immediately to the lab for freezing. The individual samples will be pooled at Mayo.

Note: If no specimen is obtained in 24 hours, extend collection to 48 - 72 hours and note time frame on request form.


Special Processing:

Lab Staff:

Blood: Centrifuge blood specimen, remove serum aliquot and place in a screw-capped plastic vial. Store and ship serum frozen.

Stool: Freeze entire stool collection and ship frozen. If the collection period had been extended, note either 48 or 72 hours on the request form.

Patient Preparation:


Sample Rejection:

Mislabeled or unlabeled specimens


Reference Range:

A1AT Clearance: ≤27 mL/24 hours

A1AT Fecal concentration: ≤54 mg/dL

A1AT Serum concentration: 100 - 190 mg/dL

Interpretation: Elevated alpha-1-antitrypsin (A1A) clearance suggests excessive gastrointestinal protein loss. (The positive predictive value of the test has been found to be 97.7% and the negative predictive value is 75%).

Patients with protein-losing enteropathies generally have A1A clearance values >50 mL/24 hours and A1A stool concentrations >100 mg/mL.

Borderline elevations above the normal range are equivocal for protein-losing enteropathies.

Critical Values:



In the absence of a 24 hour stool collection and/or a contemporary serum specimen, the fecal concentration of A1A can be used as a surrogate marker. The clearance is preferred in order to normalize the large range of serum A1A concentrations and the variability in random stool A1A concentration.




Mayo Medical Laboratories Web Page (October 2014)