Perhaps you should try some spelling variations:
"5 ppm decrease" » "5 ppm decreased" (Expand Search), "5 ppm increase" (Expand Search)
"_ point decrease" » "_ point decreased" (Expand Search), "_ point increase" (Expand Search)
"_ cd4 decrease" » "_ cd4 decreased" (Expand Search), "_ cd4 increase" (Expand Search)
"k mean decrease" » "k mean decreased" (Expand Search), "k mean increase" (Expand Search)

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("5 ppm decrease") OR ((("_ point decrease") OR ((("_ cd4 decrease") OR ("k mean decrease"))))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"5 ppm decrease\") OR (((\"_ point decrease\") OR (((\"_ cd4 decrease\") OR (\"k mean decrease\"))))))*".
• Removing quotes may allow a broader search: (( 5 ppm decrease ) OR ((( _ point decrease ) OR ((( _ cd4 decrease ) OR ( k mean decrease ))))))*.