Most commonly, rheumatoid factor is used as a blood test for the diagnosis of rheumatoid arthritis. Rheumatoid factor is present in about 80% of adults (but a much lower proportion of children) with rheumatoid arthritis.
Most flights originating from the US have a 'two piece' limit for luggage - you can check two bags, and you pay extra per bag. This applies whether the flight is domestic within the US or international. Most flights that originate from outside the US have a weight limit for total checked baggage - a miserly 20kg/44lbs if you're traveling in coach class, 30kg/66lbs for business class and 40kg/88lbs for first class.
Local restrictions on baggage weight. Please note that the maximum weight limit per single baggage is 32 kg for business class and 23 kg for economy class on all flights across the Atlantic (outbound and return, as well as transfers). Baggage exceeding this weight limit will not be accepted for check- in.