I wasn't going to reply to this as I thought the reactions of native Italians would be more useful to you, but it's just come up in an ICF I'm translating - describing the symptoms that other subjects have experienced after taking the trial drug, it says: "Pochi soggetti hanno accusato un intenso dolore alle articolazioni o al petto".

So it seems to me a completely straight term, rather than being loaded like "claim" would be in English - I doubt that any Ethics Committee would let a drugs company get away with implying in an informed consent form that previous subjects were imagining or inventing their side effects!