(redirected from a-fetoprotein)
Also found in: Dictionary, Thesaurus, Medical, Encyclopedia.


Measure of risk-adjusted performance. Some refer to the alpha as the difference between the investment return and the benchmark return. However, this does not properly adjust for risk. More appropriately, an alpha is generated by regressing the security or mutual fund's excess return on the benchmark (for example S&P 500) excess return. The beta adjusts for the risk (the slope coefficient). The alpha is the intercept. Example: Suppose the mutual fund has a return of 25%, and the short-term interest rate is 5% (excess return is 20%). During the same time the market excess return is 9%. Suppose the beta of the mutual fund is 2.0 (twice as risky as the S&P 500). The expected excess return given the risk is 2 x 9%=18%. The actual excess return is 20%. Hence, the alpha is 2% or 200 basis points. Alpha is also known as the Jensen Index. The alpha depends on the benchmark used. For example, it may be the intercept in a multifactor model that includes risk factors in addition to the S&P 500. Related: Risk-adjusted return.


1. The measure of the performance of a portfolio after adjusting for risk. Alpha is calculated by comparing the volatility of the portfolio and comparing it to some benchmark. The alpha is the excess return of the portfolio over the benchmark. It is important to Markowitz portfolio theory and is used as a technical indicator.

2. The excess return that a portfolio makes over and above what the capital asset pricing model estimates.


The mathematical estimate of the return on a security when the market return as a whole is zero. Alpha is derived from a in the formula Ri = a + bRm which measures the return on a security (Ri) for a given return on the market (Rm) where b is beta. See also capital-asset pricing model, characteristic line.


Alpha measures risk-adjusted return, or the actual return an equity security provides in relation to the return you would expect based on its beta. Beta measures the security's volatility in relation to its benchmark index.

If a security's actual return is higher than its beta, the security has a positive alpha, and if the return is lower it has a negative alpha.

For example, if a stock's beta is 1.5, and its benchmark gained 2%, it would be expected to gain 3% (2% x 1.5 = 0.03, or 3%). If the stock gained 4%, it would have a positive alpha.

Alpha also refers to an analyst's estimate of a stock's potential to gain value based on the rate at which the company's earnings are growing and other fundamental indicators.

For example, if a stock is assigned an alpha of 1.15, the analyst expects a 15% price increase in a year when stock prices are generally flat. One investment strategy is to look for securities with positive alphas, which indicates they may be undervalued.

References in periodicals archive ?
In this scoring system, we included risk factors and demographic characteristics such as age, HBsAg, HBeAg, and cirrhosis; tumor-related factors such as tumor size, vascular invasion, differentiation, encapsulation, and tumor number; and the indexes reflecting liver impairment such as a-fetoprotein, total bilirubin, partial thromboplastin time, alkaline phosphatase, and a-glutamyltransferase.
In particular, for the HCC group, a-fetoprotein was increased in only48.
Automatic and simultaneous analysis of Lens culinaris agglutinin-reactive a-fetoprotein ratio and total a-fetoprotein concentration.
Since the serendipitous finding almost 20 years ago of a reduced concentration of maternal serum a-fetoprotein (MSAFP) in an index case of a second-trimester pregnancy complicated by trisomy 18 (1) and the subsequent confirmation of this finding in other pregnancies complicated by trisomy 21, there has been a gradual improvement in trisomy 21 screening efficiency as better markers have been identified.
a-Fetoprotein (AFP), human chorionic gonadotropin (hCG) or free [beta]-hCG, and unconjugated estriol have been prospectively evaluated during the second trimester in large populations (1-11).
Application in enzyme amplified fluorimetric immunoassay for a-fetoprotein.