The eyes of the pharmaceutical industry are likely to be focused on Washington D.C. on July 20, when the Food and Drug Administration decides whether or not to give thumbs up to AstraZeneca’s (NYSE:AZN) Brilinta cardiovascular drug. That’s because the “yea” or “nay” on the drug could have far-reaching implications for an industry that continues to do a greater percentage of its clinical testing overseas.

AstraZeneca has a lot riding on approval of Brilinta. The company thinks the cardiovascular medication matches up favorably with the second best-selling drug in the world, Plavix, which generates a hefty $9 billion in sales for its owner, Bristol-Myers Squibb (NYSE:BMY).

In a large-scale global trial called Plato, Brilinta clearly outperformed Plavix in preventing cardiovascular deaths. But here’s the rub: people in North America actually seemed to do worse on the drug.  It might be because North Americans accounted for less than 10% of trial participants, and this was too small a sample to draw meaningful conclusions.

Other experts speculate that the reduced effectiveness in North America is due to that fact that many U.S. heart patients take more aspirin along with their medications. They theorize that somehow this interfered with the way Brilinta works.

The drug is already approved in more than 30 countries, including those in the European Union. Further, an FDA advisory panel endorsed Brilinta last year, which usually all but guarantees full agency approval. But given the doubts arising from the North American results, some industry analysts think that before the FDA blesses Brilinta they’re going to want to see more data. And any delay in approval is not going to be good for AstraZeneca. Neither is the uncertainty hovering over the drug’s effectiveness among North American heart patients.

The Brilinta situation is part of a larger issue: The industry’s increasing use of countries outside of North America for its drug studies, especially Eastern Europe, Asia and Latin America. In fact, in the Brilinta study, more than 20% of the patients lived in Poland and Hungary. That was more than double the percentage in the U.S. and Canada combined. That would never have been the case just a few years ago when at least half of the patients in the study would have been Americans.

Things are different today. Drug companies looking for ways to cut costs are doing more of their testing overseas, where it’s cheaper. Countries outside North America are attractive for another reason, too — the large number of what is called “treatment-naïve” patients. Simply put, these are people who aren’t taking other drugs.  It’s thought that these groups are more suitable for testing new medications.

But is the quality of the results as reliable? Many think not, pointing to the difference in lifestyles and genetics among the patients being tested. Others wonder whether ethical standards are being ignored in poorer countries in the name of cutting costs.

We’ll find out soon whether AstraZeneca’s limited North American results will cost the company? Either way, there’s a lesson to be learned here, according to two Duke Researchers who studied the Plato data. They encouraged those conducting global cardiovascular studies to strive for balanced enrollment around the world in their pivotal trials.