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- Tim R. Randolph1
- Austin Le
- Jeffrey DeMond
- ↵* Corresponding author; email: tim.randolph{at}health.slu.edu
Abstract
The objective of this study was to develop a simple, inexpensive, and rapid confirmatory test using a sodium metabisulfite microscopic method to distinguish AS from SS genotype in patients testing positive for hemoglobin S. Equal volumes of de-identified EDTA blood and 2% sodium metabisulfite were mixed, placed on a microscope slide with coverslip, and observed for sickling at 30-minute intervals over 3 hours. Sickle cells were enumerated/200 RBCs under 100x oil immersion and placed into 4 Likert categories (1+-4+) based on degree of sickling. In AS samples, 2+ and 3+ sickle cells rose most rapidly while 4+ sickle cells showed the steepest rise in the SS samples. Based on these data the number of 4+ sickle cells were counted every 30-minutes over 3 hours in 5 AS and 28 SS samples at 37 degrees Celsius. Mean number of 4+ sickle cells in AS samples were 4.75/200 at 2 hours and 17.75/200 at 3 hours whereas SS samples yielded 78.29/200 at 2 hours and 115.43/200 at 3 hours. Two-hour incubation showed a statistical difference (P=0.00024) between groups in the shortest time and may be used to distinguish SS from AS genotypes. More testing is needed to determine cutpoints to distinguish genotype.
- Received August 22, 2019.
- Accepted October 9, 2019.
- Published by American Society for Clinical Laboratory Science
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