Alpha-1-Antitrypsin Clearance, Feces and Serum

CPT CODE:

USEFUL FOR:

Diagnosing protein-losing enteropathies

SPECIMEN REQUIRED:

Feces and serum are required for this test. Blood must be drawn during the stool collection period.
SerumDraw blood in a plain, red-top tube(s) or a serum gel tube(s). Spin down and send 1 mL of serum frozen in a plastic vial.
StoolStool specimen (24 hour). Send entire collection frozen in containers (Supply T291) supplied. See "Stool Collection Information Sheet" in Special Instructions.Note:     If no specimen is obtained in 24 hours, extend collection                   to 48 to 72 hours; and note time frame on request form.

TRANSPORT TEMPERATURE:

Frozen\Ambient <14 days OK\Refrig <14 days OK

CLINICAL INFORMATION:

Alpha-1-antitrypsin (A1A) is resistant to degradation by digestive enzymesand is, therefore, used as an endogenous marker for the presence of bloodproteins in the intestinal tract. A1A clearance is reliable for measuringprotein loss distal to the pylorus.
Gastrointestinal protein enteropathy has been associated with regionalenteritis, sprue, Whipple's intestinal lipodystrophy, gastric carcinoma,allergic gastroenteropathy, intestinal lymphangiectasia, constrictivepericarditis, congenital hypogammaglobulinemia, and iron deficiencyanemia associated with intolerance to cow's milk.

CLINICAL INTERPRETATION:

Elevated A1A clearance suggests excessive gastrointestinal proteinloss. (The positive predictive value of the test has been found to be97.7% and the negative predictive value is 75%.)
Patients with protein-losing enteropathies generally have A1A clearancevalues >50 mL/24 hours and A1A stool concentrations >100 mg/mL.
Borderline elevations above the normal range are equivocal for protein-losing enteropathies.

REFERENCE VALUES:

Clearance:  < or = 27 mL/24 h

Fecal alpha-1-antitrypsin concentration:  < or =  54 mg/dL

Serum alpha-1-antitrypsin concentration:  100-190 mg/dL