Steroid use has been a serious problem in professional sports for many years now. Famous baseball players, Olympic athletes, pro wrestlers and many others have been caught using performance enhancing substances. Concern over the practice has come from fearful parents, officials from various sports leagues worried about their games' reputations, and even the United States Congress, because they have nothing more pressing to deal with.

As result of the frenzy, the World Anti-Doping Agency (WADA) has developed a relatively new measure called the biological passport designed to detect steroid use. The electronic record profiles several biomarkers which can reveal if athletes have been using drugs over a period time to improve their performances. Unlike previous drug tests, the biological passport does not directly measure substance use at one point in time.

WADA says they are confident in this new approach because it makes maintaining a drug regiment in secret far more difficult. The benefit, as Scientific American puts it, is that the test "allows investigators to see the big picture—any deviations from the rider's test-established norm that might result from doping, even if the specific drug or tactic remains unknown."

In 2008, the International Cycling Union (UCI), the governing body for professional cycling became the first organization to introduced biological passports for professional riders. Just last week, the new test helped UCI officials snag four cyclists, and earlier this year 23 others were also caught thanks to the passports. No other professional sports leagues have enacted the new testing yet, but cross-country skiing, speed skating, swimming and track and field may soon mandate that their athletes use biological passports.

While they may represent an improvement in drug testing, the passports are not unbeatable. Athletes who are determined to use performance enhancing drugs also probably do not want to be found out and will take precautions to avoid detection.

The consensus of regulators and scientists who will have to evaluate athletes passports appears to be that the tests serve as one part of the effort to rid sports of doping. Far more simple measures will be important as well, such as investigating what baseball players and cyclists are buying on the internet.