Specimen

Whole Blood

Collection Medium:

Alternate
Collection Media:

Light Green top tube (Lithium Heparin)

Minimum:

Adult Minimum:  5 mL whole blood and two unfixed smears
Pediatric Minimum:  1 mL whole blood and two unfixed smears

Rejection Criteria:

Hemolyzed specimen

Delivery Instructions:

Deliver to laboratory immediately after collection.

Analytic Time:

1 week

Reference Range:

Within normal curve limits. A graph will accompany laboratory report.

Comments:

Deliver specimen to lab before 1200 (Monday through Thursday 
only)-referred to reference laboratory.  Pertinent clinical information 
should accompany the request.  Analysis cannot be done on patients 
transfused in the preceding three months since the presence of 
transfused cells may render the interpretation ambiguous.

Osmotic fragility is run initially at reference laboratory, then sample 
is incubated for 24 hours and re-assayed.  Patient will be charged for 
2 assays.  No stat capability sent to reference laboratory.

Test
Limitations:

Spherocytes are rare in normal blood. 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 cell osmotic fragility 
test result cannot exclude an osmotic fragility abnormality since the 
osmotically labile cells may be hemolyzed and not present. Recommend 
testing during a state of prolonged homeostasis with stable hematocrit.

Methodology:

Spectrophotometry

CPT Code:

85555, 85557

See Additional Information:
Specimens Requiring Immediate Delivery