Acid Phosphatase (AP): Total and Prostatic Acid Phosphatase
Why is this test performed?
- The test is performed for the diagnosis of prostatic carcinoma by the estimation of total acid phosphatase (TAP) and the prostatic component.
- The test is also performed for the examination for the presence of semen in medicolegal cases by a vaginal swab. Due to the high level of acid phosphatase in semen, its presence indicates recent sexual intercourse. Level of ≥50 U/sample is considered as positive evidence of semen.
Collection of Sample
For the test of total acid phosphatase (TAP) and the prostatic acid phosphatase (PAP), morning sample is preferred. About 3 to 5 ml blood is collected in a vacutainer and blood is allowed to clot. Then blood is centrifuged for 10 minutes at 4500 rpm in order to get the clear serum. The test is performed immediately. However, the sample can be preserved for 24 hours if kept at 2-8º C.
- The sample has very poor stability in the whole blood, therefore serum is separated immediately and the test is performed within an hour.
- The sample is unstable for the test of ACP if the pH is more then 7.0.
- The sample is unstable for the test of ACP at room temperature (> 37º C).
- Hemolyzed serum causes the false-positive result. Increased values can be observed in hemolyzed serum.
- Total acid phosphatase (TAP)
2.5 to 3.7 ng /mL
or < 3.0 mg /L
- Prostatic acid phosphatase (PAP)
< 2.5 ng/mL (0 to 0.6 U/L)
- Other references
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
Reasons for the increased level
- Prostatic carcinoma
- Benign prostatic hyperplasia
- Metastatic carcinoma of the prostate
- Metastases to the bones
Moderately raised level seen in, other than prostatic carcinoma
- Niemann-Pick disease
- Sickle cell anemia
- Prostatitis and Benign prostatic hyperplasia ( BPH )
- Any cancer that has given metastasis to the bones.
- Urinary retention
- Multiple myelomas
- Myeloid Leukemia
- Paget disease
- Liver diseases like cirrhosis
- Renal diseases
- Gaucher’s disease
The significance of acid phosphatase test in medicolegal cases
Due to the high level of acid phosphatase in semen, its measurement is very important in rape cases. For the collection of a sample from the victim's body, following methods are applied.
- Direct aspiration or saline lavage
- Vaginal swab is obtained from the victim's vagina, and the sample is placed in 2.5% broth and can preserve at 4° C.
The significance of acid phosphatase test for the layman
- The test is performed for the diagnosis of prostatic carcinoma.
- This is carried out in cases of alleged rape or sexual assault.