No need to do a double take with the following because it is true: Shares of Intercept Pharmaceuticals (NasdaqGM: ICPT) are up $210, or a tidy 290%, after trials for the company’s liver disease treatment proved successful.

That is good news for the biotechnology sector, which is coming off another impressive run last year. The sector was so strong in 2013 that three biotech exchange traded funds were among the year’s top-10 non-leveraged ETFs.

The iShares Nasdaq Biotechnology ETF (NasdaqGS: IBB), the largest biotech ETF by assets, narrowly nudged the Market Vectors Biotech ETF (NYSEArca: BBH) for top honors among biotech ETFs last year, marking the third straight year IBB has been among the 10 best non-leveraged ETFs. [2013’s Best Health Care ETF]

But the Intercept news is benefiting another ETF: The SPDR S&P Biotech ETF (NYSEArca: XBI). XBI is up nearly 7% on volume that is well above average and has broken out to a new all-time high due in part to its 1.61% weight to Intercept.

That does not sound like much, but XBI is an equal weight ETF and none of its holdings have an allocation of more than 2.73%. XBI’s rivals IBB, BBH, the First Trust NYSE Arca Biotechnology Index Fund (NYSEArca: FBT) and the PowerShares Dynamic Biotechnology & Genome Portfolio (NYSEArca: PBE) do not hold shares of Intercept. [An ETF for Up-and-Coming Drug Developers]

Shares of Galectin Therapeutics (NasdaqGM: GALT), a rival to Intercept, is higher by 31%, but that stock is not a holding in the major biotech ETFs.

While Intercept is not an Amgen (NasdaqGM: AMGN) or Celgene (NasdaqGM: CELG) in terms of market cap heft, its surge Thursday underscores the importance of investors taking even just a few minutes to study their ETFs’ holdings.

The Intercept scenario also highlights the importance of identifying key differences between ETFs that offer exposure to the same sector or industry group. That endeavor is particularly important with biotech ETFs because in a given year, markets may favor large-cap biotechs over their small-cap brethren or vice-versa.

For example, IBB and BBH, both large-cap heavy, were 2013’s best biotech ETFs, but in2012, BBH was the leader while FBT and XBI both outpaced IBB. In 2011, IBB was the best biotech ETF while XBI held top honors in 2008.

SPDR S&P Biotech ETF