Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (674 page)

   Limitations

   Many physiologic factors affect plasma aldosterone. Posture, salt intake, use of antihypertensive drugs, use of steroids, oral contraceptives, age, stress, exercise, menstrual cycle, and pregnancy can all have a strong influence on aldosterone results.

   Licorice may mimic aldosterone effects and should be avoided 2 weeks before the test.

ALKALINE PHOSPHATASE (ALP)

   Definition

   ALP refers to a family of enzymes that catalyze hydrolysis of phosphate esters at an alkaline pH. There are at least five isoenzymes derived from the liver (sinusoidal and bile canalicular surface of hepatocytes), bone, intestine (brush border of mucosal cells), placenta, and tumor-associated tissues separated by electrophoresis. Placenta and tumor-associated ALP are the most heat resistant to inactivation. More than 95% of total ALP activity comes from the bone and liver (approximately 1:1 ratio). The half-life of ALP is 7–10 days.

   
Normal range:

   0–1 year: 150–350 IU/L

   1–16 years: 30–300 IU/L

   >16 years: 30–115 IU/L

   Use

   Diagnosis and treatment of the liver, bone, intestinal, and parathyroid diseases

   Interpretation

Increased In

   Increased bone formation