Determining Isotonicity Value involves several statements about hemolytic testing and freezing point methods. Which option is correct?

• A. ALL statements are correct
• B. Only ONE statement is correct
• C. TWO statements are correct
• D. THREE statements are correct

Answer: (C)

Isotonicity value is determined by both how a solution affects red blood cells and its overall osmotic strength. In practice, two independent checks are used: hemolytic testing, which observes whether red blood cells hemolyze or swell when exposed to the solution and thus indicates biological compatibility with blood; and the freezing point method, which measures freezing point depression to calculate the solution’s osmolality. A solution that doesn’t induce hemolysis and has an osmolality close to that of physiological fluids is considered isotonic. Because both a biological response and a precise osmotic measurement are involved, two statements among the options accurately describe valid aspects of isotonicity testing. The other options either overstate or understate the scope, such as claiming all statements are correct or relying on only one approach.