False-positive results using the solubility test may be obtained in persons with increased RBC counts as occur in polycythemias; extremely high white counts, as in some leukemias; and extremely high platelet counts. Increased levels of lipids or globulins may also cause a false-positive.
In addition to Hemoglobin S, other hemoglobins that show a positive solubility test include Hb C-Harlem, Hb C-Georgetown, and Hb C-Ziquinchor.
False-negatives in the solubility test may be obtained on persons with severely-decreased hemoglobins/hematocrits and those recently transfused. Infants less than six months old may also demonstrate false-negative results due to higher levels of Hb F.
False results in the solubility test can occur due to technical errors. False-positive results will occur if too much blood is added to the tube. False-negative results will occur if any of these errors are made:
- Too little blood added
- Use of wrong-sized test tube
- Using deteriorated reagents
- Holding the test tube too close to the background when reading result
