ACP (Acid Phosphatase) Test: Purpose, Normal Range, and High/Low Causes

What is ACP (Acid Phosphatase)?

ACP, or Acid Phosphatase, is an enzyme that helps break down phosphate compounds (phosphate esters) in an acidic environment.
It is found in many tissues of the body, but the highest amount is present in the prostate gland, especially in men.

Earlier, the ACP test was mainly used for diagnosing prostate cancer, but with the introduction of PSA (Prostate-Specific Antigen) testing, ACP is now mainly used for:

• Monitoring prostate cancer treatment and recurrence
• Detecting bone diseases and platelet disorders
• Studying lysosomal storage diseases such as Gaucher’s disease

Where is ACP Produced in the Body?

Acid phosphatase is produced in several tissues, including:

• Prostate gland – the most important source in men
• Liver
• Spleen
• Red blood cells (RBCs)
• Platelets
• Bones (osteoclasts)

Each of these tissues contributes to the total ACP activity in blood.

Main Functions and Importance of ACP

ACP plays multiple roles in different organs and medical applications:

1. Marker for Prostate Cancer

High ACP levels can indicate advanced or metastatic prostate cancer.
Although PSA is now more commonly used, ACP still helps monitor treatment response.

2. Bone Disorders

High ACP levels are found in Paget’s disease or osteolytic metastasis, where bones break down rapidly.

3. Platelet Function

ACP contributes to platelet aggregation and blood clotting functions.

4. Lysosomal Function

This enzyme is present in lysosomes, helping with intracellular digestion and waste breakdown.

5. Forensic Medicine

In forensic science, ACP testing helps detect semen in sexual assault investigations because seminal fluid contains high prostatic ACP.

Causes of Low ACP Levels

Low levels of acid phosphatase are usually not a major clinical concern.
However, they can be seen in:

• Recovery from prostate cancer after successful treatment
• Low platelet count (thrombocytopenia)

Symptoms of Low ACP Levels

Most people with low ACP do not show symptoms. The condition is often detected incidentally during lab tests.

Causes of High ACP Levels

High ACP levels indicate possible tissue or enzyme abnormalities. Major causes include:

Symptoms of High ACP Levels

The symptoms depend on the underlying cause of elevation.

If due to Prostate Cancer

• Difficulty urinating
• Weak urine flow
• Pelvic pain or lower back pain
• Bone pain (if cancer has spread to bones)

If due to Bone Disorders

• Bone pain and deformities
• Fractures or bone weakness

If due to Gaucher’s Disease

• Enlarged liver or spleen
• Bone crises (sudden bone pain)
• Fatigue and anemia

Reference Ranges of ACP

The normal range of ACP varies by lab and method, but general reference values are:

Note: Levels above these limits may indicate prostate or bone involvement.

Sample Type and Test Requirements

• Sample Type: Serum (blood sample)
• Collection Tube: Red-top (plain) tube without anticoagulant
• Test Preparation:
  • No fasting required.
  • Avoid prostate manipulation (such as digital rectal exam, biopsy, or ejaculation) for 24–48 hours before the test, as it can falsely elevate results.

Test Procedure

1. A blood sample is drawn from a vein in your arm.
2. The serum is separated and analyzed for acid phosphatase enzyme activity.
3. If needed, a specific prostatic fraction is measured separately to determine prostate involvement.

Interpretation of Results

Your doctor will always interpret results along with other tests like PSA, bone scans, or biopsy reports.

Test Preparation

• Avoid strenuous exercise before the test.
• Inform your doctor about any medications or vitamin supplements you are taking.
• Avoid any recent prostate-related examination or activity (as it can increase ACP temporarily).

When to Consult a Doctor

Consult a doctor if you experience:

• Urinary difficulties, weak urine stream, or frequent urination
• Pelvic or bone pain
• Unexplained fatigue or weight loss
• Bone deformities or fractures without injury

These symptoms could indicate underlying prostate or bone issues requiring immediate attention.

Important Word Explanations

~END~