the beta test is an hcg test to see how much of that hormone is present. many women have this done to assure their levels are doubling in pregnancy.
Excerpt from American Pregnancy Association
http://www.americanpregnancy.org/duringpregnancy/hcglevels.html
There are two common types of hCG tests. A qualitative hCG test detects if hCG is present in the blood. A quantitative hCG test (or beta hCG) measures the amount of hCG actually present in the blood.