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Leucine Aminopeptidase

This test is used to measure serum levels of leucine aminopeptidase (LAP), an isoenzyme of alkaline phosphatase (ALP) that is widely distributed in body tissues. The greatest concentrations appear in the hepatobiliary tissues, pancreas, and small intestine. Serum levels of LAP parallel serum ALP levels in hepatic disease.

Purpose

• To provide information about suspected liver, pancreatic, and biliary diseases.
• To differentiate skeletal disease from hepatobiliary or pancreatic disease.
• To evaluate neonatal jaundice.

Patient preparation

• Explain to the patient that this test is used to evaluate liver and pancreatic function.
• Tell him to fast for at least 8 hours before the test.
• Instruct the patient to stop taking drugs containing estrogen and progesterone.
• Tell the patient that this test requires a blood sample. Explain who will perform the venipuncture and when.
• Explain that he may experience slight discomfort from the needle puncture and the tourniquet but that collecting the sample usually takes less than 3 minutes.

Procedure and posttest care

• Perform a venipuncture, and collect the sample in a 7-ml red-top tube.
• Tell the patient that he may resume his usual diet and medications.

Precautions

• Handle the sample gently to avoid hemolysis.
• Transport the sample to the laboratory immediately.

Reference values

Normal values are 80 to 200 U/ml in men and 75 to 185 U/ml in women

Abnormal findings

Elevated levels can occur in biliary obstruction, tumors, strictures, and atrelin; advanced pregnancy; and therapy with drugs containing estrogen or progesterone.

Interfering factors

• Advanced pregnancy (false-high)
• Estrogen or progesterone (false-high)