This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Medicine
A crisis in a patient with sickle cell disease is most likely to be caused by 
Select and explain. 
A. Alkalosis, B. Acidosis, C. Increased oxygen concentration, D. Decreased CO2 concentration
B: Acidosis
Answer: B: Acidosis 
Explanation: A crisis in sickle cell disease occurs when deoxygenated HbS precipitates, deforming (sickling) red blood cells and .blocking capillaries. Variables that increase the propoion of ofHbS in the "deoxy" state tend to increase the probability of a crisis by increasing the extent of sickling. The "deoxy" form of hemoglobin is ored by a decrease in pH (acidosis). An increase in pH (alkalosis), increased oxygen concentration, decreased CO2 concentration and decreased 2,3-bisphosphoglycerate concentration would all or the" oxy" form of hemoglobin. Ref - Harrison's internal medicine 20e pg 692-93