It is easy for critics to slam other scientists who go out on a limb and make big claims for their work. This is the situation facing Emanuel Petricoin and Lance Liotta, two researchers with the US government. The pair led research to develop a ground-breaking diagnostic test for ovarian cancer. Their critics allege that the test is flawed and that corporate entities are trying to rush it to market anyway. The jury is still out on whether the test will prove to be useful in the clinic. But perhaps the most important aspect of the debate is that it would never have arisen if Liotta and Petricoin had not posted their data on the Internet. The episode underscores the crucial importance of readily available public data for scientific progress and, ultimately, for public health.

Liotta and Petricoin believe that their test diagnoses ovarian cancer before the disease progresses to an incurable stage. Their test uses proteomics and involves examining all the proteins in a drop of blood, scanning for a pattern that marks out cancer patients. In a widely hailed study (E. F. Petricoin et al. Lancet 359, 572–577; 2002), they claimed that their proteomic analysis was highly effective. They posted the data on which they based their conclusions on a government website, followed by two more data sets, allowing others to re-analyse their work. Other researchers have done just that, and claim to find technical problems so troubling that they question the conclusions of the original Lancet paper — and even the validity of any diagnostic test based on proteomics (see page 496).

Petricoin and Liotta have defended their methods and the integrity of proteomics as a diagnostic technique for cancer. They also say that a large clinical trial should be performed before the test is marketed to consumers. But the company that worked with the pair on the Lancet paper, Correlogic Systems, has already given two larger companies the rights to market a test called OvaCheck in the United States. Correlogic says that it has worked with its licensees, Quest Diagnostics and the Laboratory Corporation of America, to validate the test and ensure that it will work for women around the country in many different testing conditions. But the companies have not released the data on which they base this conclusion.

If OvaCheck works, it could save many women's lives. But the risks of an imperfect diagnostic test are not slight. Women who receive false positives will undergo needless stress and unnecessary surgery, whereas those who receive false negatives may not receive care in time to save their lives. Before OvaCheck hits the market, Correlogic and its licensees need to publish evidence from a large clinical trial that proves that the test works on samples collected by many different doctors around the country and the world. They should give other scientists the opportunity to examine the data and to send in blinded test samples so that they can determine for themselves whether the test gives accurate results. If it really works, the company should have every confidence that independent researchers will support their determination to speed OvaCheck into the clinic.