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?
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 RBCs
The 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).
Irreversible sickle cells are present on the peripheral smear.
Reticulocyte count is elevated
He is protected from Plasmodium falciparum.
MCHC is decreased