Summary & Overview
CPT 85557: Red Blood Cell Osmotic Fragility Test
CPT code 85557 identifies a laboratory diagnostic assay that assesses red blood cell susceptibility to hemolysis under osmotic stress. This specialized hematology test is used in the evaluation of hemolytic disorders and red cell membrane or structural abnormalities. Nationally, accurate coding and interpretation of such specialty lab tests affect clinical diagnosis, laboratory utilization, and payer coverage decisions for hematology workups.
Key payers addressed in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. The publication outlines typical sites of service (clinical and hospital laboratories), common billing considerations, and payer coverage themes. Readers will find benchmarks for utilization and reimbursement (where available), clinical context for test ordering, and policy considerations that influence payer coverage and medical necessity determinations.
The report provides a concise clinical description of the assay, guidance on typical laboratory workflow, and an overview of documentation elements payers commonly review. Data not available in the input will be explicitly noted in specific sections of the full publication.
Billing Code Overview
CPT code 85557 describes a laboratory assay that measures the degree of hemolysis of a patient’s red blood cells (RBCs) after incubation with an osmotic stressor. The test evaluates RBC fragility by exposing patient blood to a chemical agent under controlled conditions and quantifying hemolysis over a specified incubation period.
Service type: Laboratory diagnostic test
Typical site of service: Clinical laboratory or hospital laboratory
Clinical & Coding Specifications
Clinical Context
A patient presents to an outpatient hematology clinic with symptoms of chronic fatigue, jaundice, and intermittent dark urine. The clinician suspects an inherited or acquired red blood cell membrane or hemoglobinopathy causing increased red cell fragility. A peripheral blood smear and basic hemolysis panel (CBC, reticulocyte count, LDH, bilirubin, haptoglobin) are obtained. To further evaluate membrane stability and osmotic fragility, the laboratory performs the osmotic fragility test described by CPT 85557, where patient red blood cells are incubated in progressively hypotonic saline solutions and hemolysis is measured.
Typical workflow: the clinician orders the test in the electronic medical record; a phlebotomist collects a EDTA-anticoagulated blood sample; the specimen is transported to the clinical laboratory; a medical technologist or lab analyst performs the osmotic stress incubation and measures degree of hemolysis; results are reviewed by a pathologist or laboratory director and released to the ordering clinician. Results contribute to diagnosis of hereditary spherocytosis, autoimmune hemolytic anemia (as supportive data), or other membrane/hemoglobin disorders and guide further testing (e.g., EMA binding test, direct antiglobulin test, genetic testing). Typical site of service is an outpatient laboratory or hospital clinical laboratory; service type is diagnostic laboratory testing.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
00 |