the higher the bottom number, the higher the amount of ANA in the blood

normally, most people have an ANA titre of 1/40 or below. your son therefore has a raised ANA. However, this may or may not be significant.

raised ANA can be found in many diseases such as rheumatoid arthritis, Sjogren's syndrome, scleroderma, lupus, and some viral infections

however, just because ANA is raised, it doesnt mean he has any of these. in fact upto 5% of the general population have a positive ANA test.

hypothetically, think of it as something like a choleserol test. high cholesterol is found in people with heart disease BUT just because someone has raised cholesterol, that does not necessarily mean they have any disease

however it is worth keeping an eye on it. does he have any health problems (particularly joint or skin problems)?