<prompt> A 23-year-old male Subhas Raj presents to the medicine OPD with complaint of hematuria. There is no burning sensation during urination. He also has no history suggestive of respiratory tract infection. He gives a history of two of his relatives suffering from some blood disease. His coagulation studies are within normal limits. The hemoglobin electrophoresis shows the following: Hb A 60 and Hb S 40. Which of the following is most likely true about this patient?Irreversible sickle cells are present on the peripheral smear.Reticulocyte count is elevatedHe is protected from Plasmodium falciparum.MCHC is decreased  <response>: Patients who are heterozygous for the sickle cell trait Hb AS have hemoglobin composed of 35 to 40 hemoglobin S HbS; they are generally protected from sickle cell crisis, aplastic crisis and sequestration crisis by the presence of 50 normal hemoglobin H A.Amount of HbS Q is the most important factor affecting sickling of the RBCsThe alteration of the hemoglobin from HbA to HbS reduces its solubility.Patients with sickle cell trait are usually asymptomatic, although they may develop hematuria and a limited ability to concentrate urine. A high incidence of UTI and splenic infarction at high altitude may be seen. The heterozygotes enjoy relative protection from Plasmodium falciparum malaria because of increased sickling of parasitized sickle-cell trait red blood cells and accelerated removal of these cells by the splenic monocyte macrophage system.Choices A, B and D Peripheral smears are usually normal in sickle cell trait patients; irreversibly sickled cells are not seen. Furthermore, red cell indices and red cell morphology are normal; the reticulate count is not elevated. However, the sickling test will be positive RBCs will sickle when sodium metabisulfite is added. Increased MCHC, which represents intracellular dehydration, is seen only with homozygous SS i.e. full-blown sickle cell anemia. 