Hematological, Biochemical Properties, and Clinical Correlates of Hemoglobin S Variant Disorder: A New Insight Into Sickle Cell Trait

BACKGROUND: The sickle cell trait (SCT) disorder possesses a clinical heterogeneity ranging from a symptomless condition to sudden death. This study aimed to develop a diagnostic approach that helps the characterization and identification of SCT from normal subjects and sickle cell disease (SCD) patients, and to assess its severity. METHODS: Sixty controls, 24 SCD patients and 31 SCT subjects were assessed clinically, radiologically and by laboratory investigations. RESULTS: Of the SCT subjects, 12.8% were symptomatic (3.2% anemic, 6.4% hemolytic crisis, and 3.2% painful crises). Anemia was normocytic in 66.6%, and normochromic and polychromatic in 33.4%. Significantly lower red blood cells (RBCs), hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), hematocrit (Hct), Shine and Lal index (SL), and hemoglobin A (Hb A), and higher mean corpuscular hemoglobin concentration (MCHC), red cell distribution width (RDW), Ricerca index (RI), and Huber-Herklotz index (HH) were found in SCT subjects compared with the controls. Hb A and hemoglobin S (Hb S) were excellent in discriminating SCT from SCD (cut-off for SCT > 50% and < 40%) followed by Hct, MCHC, Hb, Green and King index (GK), and England and Fraser index (EF) (cut-off for SCT > 33%, > 32, > 11, < 71, and < 10, respectively). Radiologically normal findings were detected in 87% of SCT subjects; they had nearly normal liver and renal function tests (except one case each). A schematic diagnostic paradigm for SCT was proposed. CONCLUSION: This study allowed understanding of SCT in various aspects, i.e., clinical, hematological, biochemical and radiological. Thus, it could help prevention of the Hb S variant disorder and proper management of carriers. This might be applied in pre-marital screening, particularly in those with family history of Hb S disorder.