What is the primary use of blood type testing?

The primary use of blood type testing is to ensure safe blood transfusions. Blood type testing determines an individual's ABO and Rh blood group. This information is essential in medical settings, particularly in situations where a patient may require a blood transfusion. Mismatched blood types can lead to severe immune reactions, which can be life-threatening.

By identifying the correct blood type, healthcare providers can match donors and recipients accurately, minimizing the risk of transfusion reactions. This process is crucial not only for emergency transfusions but also for planned procedures where blood loss is anticipated. Therefore, blood type testing plays a vital role in patient safety during transfusions.

Other options relate to different medical contexts. Assessing hydration levels typically involves evaluating fluid balance through certain lab tests, not blood typing. Diagnosing infections usually requires the identification of pathogens rather than blood typing. Although understanding a patient's risk for disease is important in a clinical setting, it doesn’t directly pertain to the primary purpose of blood type testing. Thus, ensuring safe blood transfusions is the most relevant and significant use of blood type testing.