Test Catalog

Test Id : BAP

Bone Alkaline Phosphatase, Serum

Useful For
Suggests clinical disorders or settings where the test may be helpful

Diagnosis and assessment of severity of metabolic bone disease including Paget disease, osteomalacia, and other states of high bone turnover


Monitoring efficacy of antiresorptive therapies including postmenopausal osteoporosis treatment


The assay is not intended as a screening test for osteoporosis.


Measurements of bone turnover markers are not useful for the diagnosis of osteoporosis; diagnosis of osteoporosis should be made based on bone density.

Method Name
A short description of the method used to perform the test

Immunoenzymatic Assay

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Bone Alkaline Phosphatase, S

Lists additional common names for a test, as an aid in searching

Alkaline Phosphatase

Bone; BAP


Skeletal Alkaline Phosphatase

Specimen Type
Describes the specimen type validated for testing


Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.6 mL

Collection Instructions: Centrifuge and aliquot serum into plastic vial.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia OK

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
Frozen 90 days
Ambient 7 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

Diagnosis and assessment of severity of metabolic bone disease including Paget disease, osteomalacia, and other states of high bone turnover


Monitoring efficacy of antiresorptive therapies including postmenopausal osteoporosis treatment


The assay is not intended as a screening test for osteoporosis.


Measurements of bone turnover markers are not useful for the diagnosis of osteoporosis; diagnosis of osteoporosis should be made based on bone density.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Bone alkaline phosphatase (BAP) is the bone-specific isoform of alkaline phosphatase. A glycoprotein that is found on the surface of osteoblasts, BAP reflects the biosynthetic activity of these bone-forming cells. BAP has been shown to be a sensitive and reliable indicator of bone metabolism.(1)


Normal bone is constantly undergoing remodeling in which bone degradation or resorption is balanced by bone formation. This process is necessary for maintaining bone health. If the process becomes uncoupled and the rate of resorption exceeds the rate of formation, the resulting bone loss can lead to osteoporosis and, consequently, a higher susceptibility to fractures.


Osteoporosis is a metabolic bone disease characterized by low bone mass and abnormal bone microarchitecture. It can result from a number of clinical conditions including states of high bone turnover, endocrine disorders (primary and secondary hyperparathyroidism and thyrotoxicosis), osteomalacia, kidney failure, gastrointestinal diseases, long-term corticosteroid therapy, multiple myeloma, and cancer metastatic to the bones.(2)


Paget disease is another common metabolic bone disease caused by excessive rates of bone remodeling resulting in local lesions of abnormal bone matrix. These lesions can result in fractures or neurological involvement. Antiresorptive therapies are used to restore the normal bone structure.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.


<2 years: 25-221 mcg/L

2-9 years: 27-148 mcg/L

10-13 years: 35-169 mcg/L

14-17 years: 13-111 mcg/L

Adults: < or =20 mcg/L



<2 years: 28-187 mcg/L

2-9 years: 31-152 mcg/L

10-13 years: 19-177 mcg/L

14-17 years: 7-41 mcg/L


Premenopausal: < or =14 mcg/L

Postmenopausal: < or =22 mcg/L

Provides information to assist in interpretation of the test results

Bone alkaline phosphatase (BAP) concentration is high in Paget disease and osteomalacia.(3)


Antiresorptive therapies lower BAP from baseline measurements in Paget disease, osteomalacia, and osteoporosis. Several studies have shown that antiresorptive therapies for management of osteoporosis patients should result in at least a 25% decrease in BAP within 3 to 6 months of initiating therapy.(4,5) BAP also decreases following antiresorptive therapy in Paget disease.(6)


When used as a marker for monitoring purposes, it is important to determine the critical difference (or least significant change). The critical difference is defined as the difference between 2 determinations that may be considered to have clinical significance. The critical difference for this method was calculated to be 25% with a 95% confidence level.(1)

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Assay results should only be used in conjunction with information available from the clinical evaluation of the patient and other diagnostic procedures.


In rare cases, some individuals can develop antibodies to mouse or other animal antibodies (often referred to as human anti-mouse antibodies [HAMA] or heterophile antibodies), which may cause interference in some immunoassays. Caution should be used in interpretation of results and the laboratory should be alerted if the result does not correlate with the clinical presentation.


Liver-derived alkaline phosphatase (ALP) has some cross-reactivity in this assay: 100 U/L of liver ALP activity gives a result of 2.5 mcg/L to 5.8 mcg/L. Accordingly, serum specimens with significant elevations of liver ALP activity may yield elevated results.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Kress BC: Bone alkaline phosphatase: methods of quantitation and clinical utility. J Clin Ligand Assay. 1998;21(2):139-148

2. Kuo TR, Chen CH: Bone biomarker for the clinical assessment of osteoporosis: recent developments and future perspectives. Biomark Res. 2017 May;5:18. doi: 10.1186/s40364-017-0097-4

3. Sharma U, Pal D, Prasad R: Alkaline phosphatase: an overview. Indian J Clin Biochem. 2014 Jul;29(3):269–278. doi: 10.1007/s12291-013-0408-y

4. Kress BC, Mizrahi IA, Armour KW, et al: Use of bone alkaline phosphatase to monitor alendronate therapy in individual postmenopausal osteoporotic women. Clin Chem. 1999 Jul;45(7):1009-1017

5. Garnero P, Darte C, Delmas PD: A model to monitor the efficacy of alendronate treatment in women with osteoporosis using a biochemical marker of bone turnover. Bone. 1999 Jun;24(6):603-609

6. Raisz L, Smith JA, Trahiotism M, et al: Short-term risedronate treatment in postmenopausal women: Effects on biochemical markers of bone turnover. Osteoporos Int. 2000;11:615-620

Method Description
Describes how the test is performed and provides a method-specific reference

The instrument used is a Beckman Coulter Unicel DXI 800. The Access Ostase assay is a one-step immunoenzymatic assay used to measure bone alkaline phosphatase (BAP) in human serum. The assay utilizes a mouse monoclonal antibody specific to BAP and paramagnetic particles coated with goat antimouse antibodies. BAP in the patient's specimen binds to the anti-BAP mouse antibody, which in turn is captured by the solid phase antimouse antibody. After washing to remove any unbound material, a chemiluminescent substrate is added to the reaction vessel. The BAP present acts on the substrate to produce light, which is measured with a luminometer. The amount of light produced is directly proportional to the amount of BAP in the specimen. The amount of analyte in the specimen is determined from a stored, multipoint calibration curve.(Package insert: Access Ostase. Beckman-Coulter; 2019)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Saturday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

2 to 3 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
BAP Bone Alkaline Phosphatase, S 17838-4
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
BAP Bone Alkaline Phosphatase, S 17838-4

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports

Test Update Resources

Change Type Effective Date
Test Changes - Specimen Information 2021-10-28