Acid Phosphatase (AP), Total and Prostatic Acid Phosphatase
- It is done on the serum of the patient and performs the test within one hour.
- How to get good serum: Take 3 to 5 ml of blood in the disposable syringe or a vacutainer. Keep the syringe for 15 to 30 minutes and then centrifuged for 2 to 4 minutes to get the clear serum.
- EDTA plasma is better because it stabilizes the acid phosphatase.
- A morning sample is preferred.
- Avoid hemolysis.
- The sample is stable for 24 hours at 2 to 8 °C.
- Try to do the test immediately.
- If serum is acidified below a pH of 6.5, that will stabilize the enzyme.
- It has poor stability in whole blood.
- ACP is unstable at room temperature >37 °C.
- ACP is unstable if the pH is >7.0.
- The serum is separated immediately, and the test is performed within one hour.
- EDTA plasma is preferred that stabilizes the AP.
- Avoid prostatic massage in the last 48 hours.
- Hemolysis falsely raised the value.
- 50% of activity lost if kept at room temperature.
Purpose of the test (Indications):
- To diagnose the prostatic carcinoma by advising the estimation of Total acid phosphatase and the prostatic component.
- These two enzymes stage prostatic carcinoma and monitor the effectiveness of treatment.
- The test for acid phosphatase can be done on a vaginal swab in rape cases because the seminal fluid is rich in acid phosphatase.
- Acid phosphatase enzymes are found in various tissue lysosomes like the Prostate, bone, kidney, RBC, platelets, semen, liver, and spleen.
- High levels are also found in white blood cells like monocytes and lymphocytes.
- Acid phosphatase (AP), derived from the prostate, has a pH optimum range of 5 to 6.
- All phosphatases have optimal activity below pH of 7.0
- The difference in pH between AP and alkaline phosphatase:
Acid phosphatase Alkaline phosphatase pH 5.0 >7.0
- The greatest AP activity concentration occurs in the liver, spleen, milk, platelets, bone marrow, red blood cells, and the prostate gland.
- The prostate is the richest source. The majority of AP arises from the RBCs and prostatic tissue.
- AP enzymes are unstable, especially at a temperature above 37 °C and at a pH level of above 7.0.
- If prostate AP is left at room temperature, its 50% activity will be lost in one hour.
- As the prostatic component (PAP) is not raised in the early prostatic diseases, this is not a good screening enzyme.
- Total acid phosphatase consists of a one-half prostatic component and the rest of the liver, disintegrating platelets and RBCs.
- Acid phosphatase is a lysosomal enzyme, so the prostatic enzyme is found in the lysosome of prostatic epithelium and is a glycoprotein.
- Acid phosphatase activity is 100 times more in the prostate than other tissues, so the prostate is the richest source.
- Once prostatic cancer spreads, AP’s level starts rising and significantly raised when there is metastasis, particularly in the bone.
- The raised level in 80% of the patient with metastasis is age-related.
- It is raised in Prostatic carcinoma, particularly its prostatic component.
- Total AP is raised in Bone diseases.
- Prostatic acid phosphatase needs to be differentiated from the non-prostatic sources like RBCs source.
- Total AP = AP after tartarate inhibition = Prostatic AP.
- Total acid phosphatase
- 2.5 to 3.7 ng /mL or 2.5 to 3.7 µg/L.
- or less than 3.0 mg /L.
- Prostatic acid phosphatase = <2.5 ng/mL (0 to 0.6 U/L).
- Another reference
- Adult 0.13 to 0.63 units/L at 37 °C
- or 2.2 to 10.5 units/L (SI units).
- Child 8.6 to 12.0 units/mL at 30 °C.
- Newborn 10.4 to 16.4 units /mL at 30 °C.
Moderately raised levels seen in, other than prostatic carcinoma:
- Niemann-Pick disease.
- Gaucher’s disease.
- Prostatitis and Benign prostatic hyperplasia ( BPH ).
- Urinary retention.
- Any cancer that has given metastasis to the bones.
- Myeloid Leukemia.
- Multiple myelomas.
- Paget disease.
- Sickle cell anemia.
- Renal diseases.
- Liver diseases like cirrhosis.
The raised level is seen in:
- Significantly raised level seen in prostatic carcinoma.
- Benign prostatic hyperplasia.
- Metastatic carcinoma of the prostate.
- Metastases to the bones.
- After the surgery, its level will drop in 3 to 4 days.
- With estrogen therapy takes 3 to 4 weeks to drop the level.
- Acid phosphatase is not recommended for screening prostatic carcinoma because it’s level is not usually significantly raised until the tumor has the metastasis.
- Acid phosphatase is not advised in routine to diagnose prostatic carcinoma, in case the following parameters are recommended:
- Per-rectal digital examination.
- Transurethral ultrasound image.
- Histologic examination of the prostatic biopsy.
- Total body scan.
- The Prostatic specific antigen is advised.
- There is a high concentration in the semen, so its measurement is important in rape cases.
- Take the vaginal swab, keep it in 2.5% of broth, and store at 4 °C or room temperature.
- Result: In noncoital ladies, its value is 10 U/L and in the coital lady is >50 U/L.
- However, PSA is more specific and sensitive than acid phosphatase.
Test value for the layman:
- This test is advised for the diagnosis of prostatic cancer.
- It can be advised in case of rape on the vaginal swab.