Acid Phosphatase

Overview

Acid Phosphatase (ACP) is a hydrolytic enzyme that liberates phosphate from organic compounds under acidic pH (optimum 4–6). It is widely distributed in tissues such as the prostate, liver, spleen, red blood cells, platelets, bone, and lysosomes. ACP serves as an important diagnostic marker in prostatic, skeletal, and lysosomal disorders. The enzyme exists in several isoenzyme forms—including prostatic (PAP), lysosomal (LAP), erythrocytic (EAP), macrophage (MAP), and osteoclastic (OcAP)—each with distinct clinical significance. While historically used in prostate cancer screening, ACP also has applications in forensic science, bone metabolism studies, and genetic testing. Elevated ACP levels often indicate malignancy, bone disease, or cellular injury, making it a versatile biochemical tool.

Symptoms

(Clinical signs prompting Acid Phosphatase testing)

1. Urinary problems, such as difficulty urinating or frequent urination, possibly linked to prostate disorders.
2. Bone pain and deformities, as seen in Paget’s disease or metastatic bone lesions.
3. Fatigue, weakness, and recurrent infections, suggestive of bone marrow or hematologic abnormalities.
4. Swelling or tenderness over bones due to increased osteoclastic activity.
5. Abdominal discomfort or organ enlargement, indicating hepatic or splenic dysfunction.
6. Unexplained anemia or hemolysis, often seen in erythrocytic ACP elevation.
7. Symptoms of prostate cancer: pelvic pain, hematuria, or weight loss.
8. Signs of Gaucher’s or Niemann–Pick disease, such as hepatosplenomegaly or neurological impairment.

Causes

(Underlying conditions leading to elevated Acid Phosphatase levels)

1. Prostate carcinoma (Tartrate-labile ACP): particularly high in metastatic or advanced prostate cancer.
2. Bone diseases (Tartrate-resistant ACP): Paget’s disease, osteoclastoma, osteopetrosis, and bone metastasis.
3. Hairy cell leukemia: characterized by elevated tartrate-resistant acid phosphatase (TRAP) levels.
4. Gaucher’s and Niemann–Pick diseases: due to lysosomal dysfunction or enzyme storage defects.
5. Hyperparathyroidism: increased bone resorption raises ACP levels.
6. Hemolytic anemia: erythrocytic ACP released during red cell destruction.
7. Liver and spleen disorders: necrosis or enlargement releases hepatic/splenic ACP.
8. Prostate manipulation: transient rise after examination or surgery.
9. Forensic context: ACP acts as a semen marker in sexual assault investigations.

Risk Factors

(Groups at higher risk of abnormal ACP activity)

1. Men over 50 years, more prone to prostate disorders and carcinoma.
2. Patients with known skeletal diseases, such as Paget’s disease or osteoporosis.
3. Individuals with lysosomal storage diseases, including Gaucher’s and Niemann–Pick.
4. Cancer patients, especially those with metastasis to bone or prostate malignancies.
5. Patients undergoing prostate surgery or biopsy, as mechanical manipulation temporarily elevates ACP.
6. Individuals with chronic hemolytic anemia, where red blood cell destruction increases ACP release.
7. Postmenopausal women, who may show altered bone turnover affecting ACP levels.
8. Forensic and medicolegal cases, where ACP detection helps confirm semen presence.

Prevention

(Measures to ensure accurate testing and control of ACP-related conditions)

1. Proper sample collection and handling:
   1. Collect 3ml venous blood in a plain red-capped tube.
   2. Allow blood to clot at room temperature and centrifuge promptly to separate serum.
   3. Avoid hemolysis and refrigeration—hemolyzed or refrigerated samples are unsuitable.
   4. Serum samples are stable for one month if frozen.
2. Analytical methods: Employ ELISA, chemiluminescence immunoassay, or colorimetric techniques for precise ACP quantification.
3. Monitor both total and prostatic ACP fractions:
   1. Total ACP indicates systemic or skeletal pathology.
   2. Prostatic ACP is more specific for prostate-related conditions.
4. Reference ranges:
   1. Adult males: 0–5.4 U/L
   2. Adult females: 0–3.5 U/L
   3. Children: 8.6–12 U/L (due to growth)
   4. Prostatic fraction: 0.0–3.5 ng/mL
5. Regular prostate screening: For men over 50 or those with urinary symptoms, periodic ACP and PSA testing are recommended.
6. Prevent confounding factors: Avoid vigorous physical activity or prostate manipulation before testing.
7. Disease management: Treating underlying disorders like cancer, bone disease, or lysosomal dysfunction can normalize ACP levels.
8. Clinical interpretation: Elevated ACP should always be evaluated in conjunction with clinical findings and PSA levels to confirm diagnosis.