Laboratory analyses of erythrocyte hydration. (A) Incubated osmotic fragility. Osmotic fragility curves in OHSt and HX. The shaded region is the normal range. Diagrammatic representation of both OHSt (blue) and HX (red) curves is shown. (B) Osmotic gradient ektacytometry. Characteristics of erythrocyte dehydration in HX include mildly reduced deformability index with a leftward shift of the minimal osmolality point (Omin, the osmolality yielding release of 50% of hemoglobin reflecting the surface area to volume ratio of erythrocytes) and a leftward shift of the maximal osmolality point (which contains Ohyper or O′). In OHSt, the deformability index is normal or nearly normal and the minimal and maximal osmolality points are shifted to the right.