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.
Checked Luggage. These sizes are the most popular size of luggage to check. They are ideal for trips of 5 to 7 days, or longer, depending on how you pack. They have a large capacity for multiple outfits, shoes, and toiletries.1 - 22 Carry-on Luggage. These are the most popular sizes of carry-on luggage for U.S. domestic flights. Most U.S. airlines have carry on restrictions of 22 x 14 x 9, or 45 linear inches.