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CPT®
85540

CPT® Code 85540

Official Description

Leukocyte alkaline phosphatase with count

© Copyright 2025 American Medical Association. All rights reserved.

Common Language Description

The CPT® Code 85540 refers to a laboratory test that measures leukocyte alkaline phosphatase (LAP), which is an enzyme found in white blood cells (WBCs), also known as leukocytes. This enzyme plays a role in various physiological processes, and its levels can provide important diagnostic information. Although the use of this test has diminished due to the advent of more advanced diagnostic techniques, it remains relevant in specific clinical scenarios. The LAP test is particularly useful in differentiating chronic granulocytic leukemia from a leukemoid reaction, which is characterized by an elevated white blood cell count that is not due to infection or malignancy. Additionally, this test can aid in the evaluation of patients with conditions such as polycythemia vera, myelofibrosis, aplastic anemia, pernicious anemia, and essential thrombocytopenia. To perform the test, a blood sample is collected through a venipuncture, which is a separately reportable procedure. The whole blood sample is then analyzed under a microscope, utilizing enzyme assays and/or cytochemical stains to assess the levels of leukocyte alkaline phosphatase.

© Copyright 2025 Coding Ahead. All rights reserved.

1. Indications

The leukocyte alkaline phosphatase test (CPT® Code 85540) is indicated for the following conditions:

  • Chronic Granulocytic Leukemia - The test helps in differentiating this type of leukemia from other conditions that may present with similar symptoms.
  • Leukemoid Reaction - This test is useful in identifying elevated white blood cell counts that are not caused by infection or malignancy.
  • Polycythemia Vera - The LAP test can assist in the evaluation of this blood disorder characterized by an increased number of red blood cells.
  • Myelofibrosis - This condition, which involves the scarring of bone marrow, can also be assessed using the LAP test.
  • Aplastic Anemia - The test may be utilized in the evaluation of this disorder where the bone marrow fails to produce sufficient blood cells.
  • Pernicious Anemia - The LAP test can aid in the assessment of this type of anemia caused by vitamin B12 deficiency.
  • Essential Thrombocytopenia - This condition, characterized by an elevated platelet count, may also be evaluated using the LAP test.

2. Procedure

The procedure for conducting the leukocyte alkaline phosphatase test involves several key steps:

  • Step 1: Venipuncture - A blood sample is obtained from the patient through a venipuncture, which is a procedure where a needle is inserted into a vein to collect blood. This step is crucial as it provides the whole blood sample needed for the test.
  • Step 2: Sample Preparation - Once the blood sample is collected, it is prepared for analysis. This may involve mixing the sample to ensure that the components are evenly distributed.
  • Step 3: Microscopic Examination - The prepared whole blood sample is then examined under a microscope. This examination allows for the assessment of leukocyte alkaline phosphatase levels.
  • Step 4: Enzyme Assay and/or Cytochemical Staining - The analysis may include the use of enzyme assays and/or cytochemical stains to accurately measure the levels of LAP in the leukocytes. These techniques help in identifying the enzyme activity and provide valuable diagnostic information.

3. Post-Procedure

After the leukocyte alkaline phosphatase test is completed, the patient may experience minimal discomfort at the venipuncture site, which typically resolves quickly. There are no specific post-procedure care instructions required for this test, but patients should be advised to monitor the site for any unusual symptoms, such as excessive bleeding or signs of infection. The results of the test will be analyzed and interpreted by a qualified healthcare professional, who will discuss the findings with the patient and determine any necessary follow-up actions based on the results.
Short Descr WBC ALKALINE PHOSPHATASE
Medium Descr WBC ALKALINE PHOSPHATASE COUNT
Long Descr Leukocyte alkaline phosphatase with count
Status Code Statutory Exclusion (from MPFS, may be paid under other methodologies)
Global Days XXX - Global Concept Does Not Apply
PC/TC Indicator (26, TC) 9 - Not Applicable
Multiple Procedures (51) 9 - Concept does not apply.
Bilateral Surgery (50) 9 - Concept does not apply.
Physician Supervisions 09 - Concept does not apply.
Assistant Surgeon (80, 82) 9 - Concept does not apply.
Co-Surgeons (62) 9 - Concept does not apply.
Team Surgery (66) 9 - Concept does not apply.
Diagnostic Imaging Family 99 - Concept Does Not Apply
CLIA Waived (QW) No
APC Status Indicator Conditionally packaged laboratory tests
Type of Service (TOS) 5 - Diagnostic Laboratory
Berenson-Eggers TOS (BETOS) T1H - Lab tests - other (non-Medicare fee schedule)
MUE 1
CCS Clinical Classification 233 - Laboratory - Chemistry and Hematology
90 Reference (outside) laboratory: when laboratory procedures are performed by a party other than the treating or reporting physician or other qualified health care professional, the procedure may be identified by adding modifier 90 to the usual procedure number.
Date
Action
Notes
Pre-1990 Added Code added.
Code
Description
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