What this test measures
Acid phosphatase is a family of enzymes active in acidic environments, produced principally by the prostate gland, osteoclasts (bone-resorbing cells), red blood cells, platelets and the spleen. The lab measures the total enzyme activity in serum and, in some panels, splits out the prostatic fraction (PAP) and the tartrate-resistant fraction (TRAP).
In current practice, prostate-specific antigen (PSA) has largely replaced PAP for prostate cancer screening and monitoring. Acid phosphatase still has a niche role in evaluating metastatic prostate cancer, certain bone diseases (Paget's, hairy cell leukaemia where TRAP rises), Gaucher disease, and in forensic medicine.
Why it matters
In India, where prostate cancer incidence is rising in older men and screening uptake is still low, acid phosphatase is occasionally requested when PSA is unavailable or to support a metastatic workup. The test has limited stand-alone diagnostic value today, but it remains useful when interpreted alongside PSA, imaging and bone markers.
A persistently raised acid phosphatase in a man over 50 warrants a focused prostate evaluation. Markedly elevated values can also appear in Gaucher disease (relevant in some Indian Jewish and other communities), multiple myeloma with bone involvement, and hairy cell leukaemia.
How to prepare
No fasting required. Avoid a digital rectal examination (DRE), prostate massage, cystoscopy or vigorous bicycle riding in the 48 hours before the sample — all can transiently elevate prostatic acid phosphatase. Sample must be processed promptly (the enzyme is unstable at room temperature) — confirm with the lab.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Total Acid Phosphatase (U/L)[1][2] | 0 – 6.5 (varies by method; check lab range) | Low values are not clinically significant. | Raised total acid phosphatase suggests metastatic prostate cancer (especially with bone metastases), Paget's disease of bone, hyperparathyroidism, hairy cell leukaemia, Gaucher disease, multiple myeloma, or haemolysis (red cell source). Mild rises can follow recent DRE, cystoscopy or prostatic surgery. |
| Prostatic Acid Phosphatase (PAP) (ng/mL) | 0 – 3.5 | Not clinically significant. | Elevated PAP suggests prostatic disease — most concerning for metastatic prostate cancer. Mild rises can follow benign prostatic hyperplasia (BPH), prostatitis, or recent prostatic manipulation. PSA is more sensitive for early disease; PAP is more useful in advanced / metastatic disease. |
Acid phosphatase vs PSA — when each is used
| Marker | Best use | Sensitivity (early prostate cancer) | Stability |
|---|---|---|---|
| PSA (Total) | Screening, early detection, post-treatment monitoring | High | Stable; standard of care |
| Prostatic Acid Phosphatase (PAP) | Metastatic prostate cancer, salvage marker when PSA unavailable | Low | Enzyme unstable; needs prompt processing |
| Total Acid Phosphatase | Bone disease (Paget's, metastases), Gaucher, hairy cell leukaemia | Non-specific | Enzyme unstable |
| Bone-specific ALP | Paget's, bone metastases | Moderate | Stable |
Frequently asked questions
Is acid phosphatase still used to screen for prostate cancer?
No. PSA has replaced it for screening and early detection. Acid phosphatase is now mainly used in advanced or metastatic prostate cancer, in some bone diseases, and where PSA is unavailable.
Do I need to fast?
No fasting is required. But avoid digital rectal examination, prostate massage or cycling in the 48 hours before — they can transiently raise the value.
My acid phosphatase is raised but PSA is normal. What does that mean?
Possibilities include benign prostate enlargement, recent prostatic manipulation, a non-prostatic source (bone disease, Gaucher, hairy cell leukaemia, haemolysed sample), or laboratory artefact. Your doctor will correlate with symptoms and may repeat with proper sample handling.
How quickly does the sample need to be processed?
Acid phosphatase is unstable at room temperature — the sample must be processed within 1–2 hours or acidified for transport. A delayed sample can give falsely low results.
Can women have this test?
Yes — when investigating bone disease, Gaucher disease, hairy cell leukaemia, or haematological conditions. There is no "prostate" relevance in women.
Does prostatitis raise acid phosphatase?
Yes, acute prostatitis and even vigorous prostate massage can produce mild rises. The value usually settles after the infection resolves.
Related Liver / Enzymes tests
Tests commonly ordered alongside ACID PHOSPHATASE, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — Acid Phosphatase Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Acid Phosphatase · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Laboratories — Acid Phosphatase, Serum · accessed 2026-05-30T00:00:00.000Z
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