Alkaline Phosphatase (ALP): Potential Sources of Error in your Lab Result

What is the Alkaline Phosphatase (ALP) test?

An alkaline phosphatase (ALP) test measures the amount of ALP in your blood. Where is this enzyme found in the body? ALP is an enzyme found in many parts of your body. Each part of your
body produces a different type of ALP. Most ALP is found in your liver, bones, kidneys, and digestive system.

What can abnormally high or low blood ALP results mean?

Abnormal levels of ALP in your blood may be a sign of a wide range of health conditions, including liver disease, bone disorders, and chronic kidney disease. Alkaline phosphatase test alone can’t identify the source of ALP in your blood, so other tests are usually needed to make a diagnosis.

What if the ALP result is high?

If your test results show high ALP levels, your provider may order other tests to help figure out what’s causing the problem. These other tests include; An ALP isoenzyme test which can tell which part of your body is making the ALP or liver function tests. If these test results are also high, then your high ALP level then it is likely a problem in your liver.

When can ALP be ordered by your PCP / NP?

An alkaline phosphatase test is often used to screen for or help diagnose diseases of the liver or bones.
The test may also help diagnose or monitor other health conditions.

Are there any interfering supplements that could alter ALP results?

Yes, there are, and these interfering substances can either increase ALP activity or concentration
Prescription medications: There are many drugs that may result in a raised alkaline phosphatase. It is important to consider that a medication may be the cause of an isolated raised alkaline phosphatase.

Some drugs that can lower ALP levels include: oral contraceptives, hormone replacement therapy, Cinacalcet

Some drugs that may cause a raised ALP include:
Antibiotics: penicillin derivatives, nitrofurantoin, erythromycin, aminoglycosides, sulfonamides, trimethoprim-sulfamethoxazole.
Antiepileptic drugs: Carbamazepine, Phenobarbital, Phenytoin, Valproic Acid
Antihistamines: Cetirizine,
Cardiovascular drugs: Captopril, Diltiazem, Felodipine, Verapamil, Quinidine, Flutamide.
Disease-modifying agents: Penicillamine, Sulfa drugs, Gold salts.
Polycyclic aromatic hydrocarbons: Estrogens, Anabolic Steroids, Steroids, Methyltestosterone.
Psychotropic drugs: Monoamine oxidase inhibitors, Phenothiazines e.g. chlorpromazine.
Diabetes drugs: tolbutamide, chlorpropamide, tolazamide
Other drugs: Allopurinol, Methimazole, Disulfiram, Phenylbutazone

Over-the-counter medications (OTC) that interfere with ALP:

Magnesium deficiency, zinc deficiency, vitamin B12 deficiency, and excess vitamin D intake, can either lower ALP activity or concentration in the blood.

Test method-related interferences that affect ALP results:

A high concentration of bilirubin can cause a false low measurement of ALP levels.

Other disease conditions that:

Wilson’s disease causes patients to have low blood alkaline phosphatase activity and enzyme concentration.
An underactive thyroid (hypothyroidism), excess cortisol levels (Cushing’s syndrome), and anemia (that can be related to vitamin B12 deficiency) can lower ALP levels.

Are there any lifestyle-related activities that can interfere with ALT results?

Malnutrition and people on a protein-free diet, are at risk of low ALP. Pregnant women have higher blood ALP activity levels while cigarette smoking raises ALP.

What do you say to your primary care physician (PCP)?

Tell your PCP about the OTC, prescription, and/or herbs you are taking. Especially if you see more than one clinician because drugs prescribed by another Clinician can have drug-drug interactions. Also, if your clinician is unaware of your smoking or alcohol habits, be sure to let your PCP know, in order to optimize your healthcare and treatment.

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