Complex sentence: Most people are diagnosed without symptoms as the result of a routine blood test that returns a high white blood cell count, but, as it advances, CLL results in swollen lymph nodes, spleen, and liver, and eventually anemia and infections.
Split into simpler sentences: Most people are diagnosed without symptoms as the result of a routine blood test that shows a high white blood cell count. As it advances, CLL results in swollen lymph nodes, spleen, and liver, and eventually anemia and infections.