Need help choosing the right code?
Ask CasePilot about procedures, modifiers, bundling, and coding guidance.
Try CasePilot© Copyright 2026 American Medical Association. All rights reserved.
Hydroxyproline is classified as a non-protein amino acid that is predominantly found in collagen, a vital protein that provides structure and strength to various tissues in the body, including skin, bones, and cartilage. The measurement of hydroxyproline levels can be significant in diagnosing and monitoring certain medical conditions. Elevated levels of hydroxyproline may indicate pathological conditions such as Paget's disease, which involves abnormal bone remodeling, bone metastatic cancer, where cancer spreads to the bones, hyperparathyroidism, a condition characterized by excessive parathyroid hormone production leading to increased calcium levels, osteoporosis, a disease that weakens bones, or glucocorticoid excess, which can affect bone metabolism. Although hydroxyproline testing can serve as a non-specific marker for bone resorption, it is important to note that newer and more specific tests are now available. The testing process for hydroxyproline involves measuring free hydroxyproline levels in the blood, which requires a blood specimen obtained through venipuncture. This specimen undergoes quantitative analysis using high-performance liquid chromatography (HPLC) on blood plasma or serum. Additionally, hydroxyproline levels can also be assessed through urine testing, where patients must adhere to a collagen-free diet for 72 hours prior to urine collection. A 24-hour urine specimen is then collected and analyzed using colorimetric methodology. Furthermore, the total hydroxyproline in urine can be evaluated under CPT® Code 83505, which also necessitates the same dietary restrictions and collection methods.
© Copyright 2026 Coding Ahead. All rights reserved.
Hydroxyproline testing is indicated for the evaluation of various medical conditions that may affect bone metabolism and collagen turnover. The following conditions may warrant the measurement of hydroxyproline levels:
The procedure for measuring hydroxyproline involves several key steps to ensure accurate results. The first step is obtaining a blood specimen, which is performed through a venipuncture. This procedure requires a trained healthcare professional to insert a needle into a vein, typically in the arm, to collect blood. The collected blood is then processed to separate the plasma or serum, which is necessary for the quantitative analysis of free hydroxyproline levels. This analysis is conducted using high-performance liquid chromatography (HPLC), a sophisticated technique that allows for precise measurement of the hydroxyproline concentration in the blood sample.
In addition to blood testing, hydroxyproline levels can also be assessed through urine testing. For this method, patients must adhere to a collagen-free diet for 72 hours prior to urine collection to avoid any dietary influences on the test results. A 24-hour urine specimen is then collected, which involves collecting all urine produced over a full day. This specimen is analyzed using colorimetric methodology to measure free hydroxyproline levels. Furthermore, for the evaluation of total hydroxyproline in urine, CPT® Code 83505 is utilized, which also requires the same dietary restrictions and collection process, but may employ different analytical techniques such as ion exchange chromatography or high-performance liquid chromatography.
After the hydroxyproline testing procedure, there are no specific post-procedure care requirements for patients. However, it is essential for patients to follow any additional instructions provided by their healthcare provider regarding diet or medication that may affect future testing. Results from the hydroxyproline tests should be interpreted in conjunction with clinical findings and other diagnostic tests to provide a comprehensive assessment of the patient's bone health and metabolic status.
| Short Descr | ASSAY FREE HYDROXYPROLINE | Medium Descr | ASSAY OF FREE HYDROXYPROLINE | Long Descr | Hydroxyproline; free | 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
|
|---|---|---|
| 2023-01-01 | Note | Medium description changed. |
| 2013-01-01 | Changed | Medium Descriptor changed. |
| 2011-01-01 | Changed | Short description changed. |
| Pre-1990 | Added | Code added. |
Get instant expert-level medical coding assistance.