Lab Test

Sickle Cell Screen

Sickle cell preparation, Sickle prep, Dithionite test, Sickledex, Hemoglobin S Solubility, Sickle Cell

Test Codes





A sickle cell test screens for sickle cell trait or sickle cell disease in people at high risk. The sickle cell test does not need to be repeated once it is positive. Samples submitted for patients who have already had a positive Sickle Cell Screen will not be performed.

Specimen Collection Criteria

Collect (preferred specimen): One 4.0 mL Lavender-top K2EDTA tube. (Minimum: 2.0 mL)
Also acceptable: One Lavender-top K2EDTA Microtainer® (Minimum: 300 mcL), Gray-top Sodium or Potassium Oxalate tube, Light Blue-top Sodium Citrate tube, Green-top Heparin tube, Yellow-top ACD tube, or a tube containing CPD or CPDA-1.

See Minimum Pediatric Specimen Requirements for Microtainer® collection.

Physician Office/Draw Specimen Preparation

Maintain specimen at room temperature (20-26°C or 68-78.8°F) or refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Transport: Whole blood or capillary blood at room temperature (20-26°C or 68-78.8°F) or refrigerated (2-8°C or 36-46°F). (Minimum: 2.0 mL whole blood or 300 mcL capillary blood)

Rejection Criteria

  • Insufficient volume.
  • Frozen specimens.
  • Samples submitted for patients previously determined to have a positive sickle cell test.

In-Lab Processing

For more information on this test please see procedures at 


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 5 days
Refrigerated (2-8°C or 36-46°F): 5 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days


Dearborn Blood Bank Laboratory
Farmington Hills Hematology Laboratory
Grosse Pointe Hematology Laboratory
Royal Oak Hematology Laboratory
Troy Blood Bank Laboratory


Sunday – Saturday.
Results available within 24 hours.

Reference Range


Test Methodology



The estimated frequency of Hgb S/S in the U.S. population is one in four thousand (0.025%) and one in one hundred (1%) for the heterozygous genotype. The homozygous form of Sickle Cell Disease affects 0.3% of the African American population. The heterozygous form of the disease (sickle cell trait) affects more than 8% of the African American population.

Since the Sickledex method is a qualitative test and does not distinguish between Sickle Cell Disease (S/S) and heterozygous Hgb S syndromes (e.g., A/S, C/S, etc.), all positive tests should be further evaluated by hemoglobin electrophoresis.

False negatives may occur if:

  1. Hgb S concentration is low in infants younger than 6 months of age (due to the presence of Hgb F) and in transfused patients where the Hgb S is diluted below 30%.
  2. Anemia (Hgb < 15%). 

False positives may occur if:

  1. Abnormal proteins, abnormal elevations of total serum proteins (particularly gamma globulins), and hyperlipidemia.
  2. Hgb CHarlem, Hgb CGeorgetown, Hgb STravis, and Hgb CZiguinchor.
  3. Transfusions with Hgb S blood.
  4. Extremely high hemoglobin, erythrocyte count, or leukocyte count.
  5. Many Heinz bodies in unstable hemoglobin disorders after splenectomy.

Clinical Utility

This assay is used to screen for hemoglobin S (sickle cell trait).

CPT Codes



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