Osmotic Fragility, RBC

Abbrev Code:OSMFRA   
Order Code:LAB1134Order Name:Fragility Test Osmotic
Synonyms:RBC Osmotic Fragility; Red Cell Fragility
CPT Codes: 85555 x1
Turnaround Time:Specimens are sent to reference laboratory Mon-Sat; results are reported in 1-5 days.

For tests that use an in vitro diagnostic (IVD) that has been cleared or approved by the FDA.

Collection Instructions

Specimen:Blood and smears
Optimal Volume:5 mL
Minimum\Peds Volume:1 mL
Container:Green (sodium heparin, no gel)
Alternate Containers: Green (lithium heparin, no gel), Purple (EDTA)
Collection Instructions:Immediately mix specimen 10 times by gentle inversion. Also send 2 smears made from blood being submitted. Refrigerate within 30 minutes of collection.
Causes for Rejection:Clotted specimen, hemolyzed specimen, specimens greater than 72 hours old.

Processing and Shipping

Specimen Processing:Do not store. Send whole blood and 2 smears made with blood being submitted.
Shipping Instructions:Ship at refrigerated temperature.
Stability:72 hours at refrigerated temperature.
Test Performed at or Referral Lab Lab Sendouts  (ARUP)
Referral Lab number:2002257


Reference Range:Within normal curve limits.

Erythrocyte osmotic fragility is most often requested in the work-up of possible cases of hereditary spherocytosis (HS). When spherocytes are suspected on the basis of an elevated mean corpuscular hemoglobin concentration or on examination of a peripheral blood smear, the osmotic fragility test may be used to confirm the presence of spherocytes. The test does not distinguish between spherocytes in HS and in acquired autoimmune hemolytic anemia; the test only indicates that a proportion of the red cells have decreased surface-to-volume ratios and are more susceptible to lysis in hypo-osmotic solutions. HS patients who are experiencing significant elevations in reticulocytes may not fall outside of the normal range. Cells with increased surface-to-volume ratios, such as occur in thalassemias and iron deficiency, may show decreased osmotic fragility.


For patients with acute hemolysis, a normal red blood cell osmotic fragility test result cannot exclude an osmotic fragility abnormality since the osmotically labile cells may be hemolyzed and not present. Testing during a state of prolonged homeostasis with stable hematocrit is recommended.


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