Alpha 1 Antitrypsin Clearance, Feces & Serum (Sendout)

Useful For: Diagnosing protein-losing enteropathies.

Ordering Note: This test is for timed stool collections only and requires serum to be collected during the stool collection period. For testing on random stool samples, refer to separate test Alpha 1 Antitrypsin, Random Stool (Sendout) [RSA1A].

Reference Values:

Interpretation:

Elevated alpha-1-antitrypsin (AAT) 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 AAT clearance values greater than 50 mL/24 hours and AAT fecal concentrations above 100 mg/dL.

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

Cautions:

In the absence of either a 24-hour fecal collection or a contemporary serum specimen, the fecal concentration of alpha-1-antitrypsin (AAT) can be used as a surrogate marker. The clearance test is preferred as it normalizes the large range of serum AAT concentrations and the variability in random fecal AAT concentrations.

When gastric loss of AAT is suspected (eg, Menetrier disease), AAT clearance is not a reliable indicator of protein loss as AAT is sensitive to pH <3 and rapidly destroyed. When gastric protein loss is suspected and the AAT clearance is normal, the recommendation is to repeat testing after starting an acid suppressive medication regime.

Collection Note: This test requires both a timed stool collection and a blood collection. Collections must be timed appropriately to prevent rejection at Mayo.

Stool: Stool collected in Mayo Stool Container(s) [Supply T291]* for 24 to 72 hours.

• Collect a 24-hour stool collection.
• If a blood sample is not obtained within 24 hours, extend stool collection time to 48 to 72 hours and collect blood within this window.
• Label individual containers with the order of collection (ex: 1 of 2, 2 of 2). Send all containers.
• Document the collection interval on the requisition.

*Mayo stool containers are preferred because they can accommodate the entire timed collection. However, if Mayo containers are not available, samples may be submitted in alternative screw-cap, preservative-free stool containers.

Blood: 3 mL Blood in RED TOP or GOLD SST

• Blood must be drawn during the stool collection period.

Stool Kits:

• Obtain Mayo stool containers at HMC Laboratory (Room GWH-47) or UW Montlake Laboratory (Room NW-220).
• Mayo recommends 1 "kit" (bag of 2 containers) for every 24 hours of collection.

Outside Laboratories:

• Blood: Centrifuge sample and transfer serum to a separate plastic vial within 2 hours of collection. Freeze serum at -20°C while awaiting transport. Ship on dry ice.
• Stool: Label stool containers appropriately with two patient identifiers and the order of collection (1 of 2, 2 of 2, etc.). Freeze the entire stool collection at -20°C while awaiting transport. Ship on dry ice.
• Indicate the stool collection interval on the DLMP requisition.
• Stool and blood samples must arrive together in the laboratory.

Stability:

• Stool: Frozen (preferred): 14 days; Refrigerated 14 days; Ambient: 14 days.
• Serum: Frozen (preferred): 28 days; Refrigerated: 28 days; Ambient: 28 days.

Reject Due To:

• Serum: Gross hemolysis, gross lipemia, or gross icterus.
• Stool: Feces collected in any preservative or fixative.

• Blood: Centrifuge sample and transfer serum to a separate plastic vial within 2 hours of collection. Freeze serum at -20°C.
• Stool: Freeze entire stool collection at -20°C. Samples cannot be shared.

Login: SEND1-;FREEZE

• RSNDT1: MAYOSD
• RSTYP1: STL-SERUM
• RTSRQ1: ;Alpha 1 Antitrypsin Clearance, Stool and Serum (Mayo Test A1AFS)

Sendouts:

• Hold the serum sample until the stool samples are received in lab. Stool and serum samples should be shipped to Mayo together to prevent delays or cancellations.
• Order Mayo Test: A1AFS.
• MayoAccess Order Question: Enter the total collection interval in hours.

Stability:

• Stool: Frozen (preferred): 14 days; Refrigerated 14 days; Ambient: 14 days.
• Serum: Frozen (preferred): 28 days; Refrigerated: 28 days; Ambient: 28 days.

Reject Due To:

• Serum: Gross hemolysis, gross lipemia, or gross icterus.
• Stool: Feces collected in any preservative or fixative.