Medical Laboratory Scientist ASCP Practice Exam 2026 – Complete Study Guide

The sickling phenomenon in erythrocytes that contain hemoglobin S (HbS) is primarily influenced by the polymerization of hemoglobin under certain physiological conditions. This process can be triggered by various factors, with the most significant being low oxygen levels (hypoxia), dehydration, and acidosis.

Low pH, which indicates acidosis, is known to promote the sickling of red blood cells. A decrease in pH results in increased hydrogen ion concentration, which causes the hemoglobin to shift from its oxygenated to deoxygenated state more readily. This decreased presence of oxygen leads to the formation of polymers of HbS, resulting in the characteristic sickling of erythrocytes.

Oxidizing agents can also contribute to sickling by promoting the formation of methemoglobin, which reduces the overall oxygen-carrying capacity of hemoglobin, thus leading to conditions that favor sickling. However, the effect of reducing agents is generally opposite, as they prevent oxidation and maintain hemoglobin in its functional reduced form, thereby reducing sickling tendencies.

High temperatures can destabilize the hemoglobin structure but do not directly influence the sickling phenomenon in the same manner that acidosis does.

Therefore, considering the metabolic and biochemical environments within the body