Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:When we combine the results of these two studies in pancreatic and gastric cancer patients, we can say that HDL and PON1 levels are lower in cancer patients than in control subjects (Akcay et al., 2003a,b).
Category: