Disappointment. That's the common denominator on this week's list of horrendous performers in health care.\: They all had disappointments of one type or another. Here they are -- three of the worst health-care stocks over the past week.

Disappointing FDA request
High-flying Sarepta Therapeutics (SRPT -1.26%) encountered some turbulence this week. Shares in the biotech fell more than 18%.

Some investors were apparently banking on Sarepta's eteplirsen, an experimental drug targeting treatment of rare disease Duchenne muscular dystrophy, to sail through the Food and Drug Administration's accelerated approval process. However, this week Sarepta announced that the FDA requested additional information.

As I wrote earlier this week, there are two different perspectives on the FDA request. The negative view is that accelerated approval is unlikely if the FDA wasn't convinced by Sarepta's information already provided. Positive thinkers suggest that the FDA request could mean good news, because it's already asking the kinds of questions usually reserved for the regulatory review itself.

Disappointing test results
Exact Sciences (EXAS 2.35%) announced preliminary results from a study of its Cologuard colorectal cancer screening test on Thursday. All of the primary and secondary endpoints from this study were met, but Exact shares still dropped 13%. Where was the disappointment?

The issue for Exact was that Cologuard showed only 42% sensitivity for finding pre-cancerous polyps. Many expected the DNA test to have a pre-cancer detection rate of 50% or higher.

Kevin Conroy, CEO of Exact Sciences, downplayed the disappointing results, saying that "clinically it just won't make much of a difference." The company emphasized the good news from the study, including a 92% sensitivity for the detection of colorectal cancer.

Disappointing status quo
Sometimes the most disappointing news is no news at all. That's the story for Amarin (AMRN 3.15%). Shares dropped 11% as investors appeared to experience a bit of malaise.

Many had hoped that by now, Amarin would have good news on possible New Chemical Entity, or NCE, status for cholesterol drug Vascepa. Those hopes haven't been fulfilled. The FDA's Orange Book update last Friday underscored the lack of progress by listing Vascepa by commenting, "There is no unexpired exclusivity for this product."

Lack of NCE status for Vascepa isn't nearly as important as FDA approval for the drug's usage by patients with less severe levels of triglycerides. However, speculation abounds that potential partnerships for Amarin hinge on NCE status.

Encouraging
With all of these disappointments, can investors gain encouragement from any of these stocks? I think so.

The possibility for accelerated approval still exists for Sarepta. Even if that doesn't materialize, the long-term prospects for the stock look good.

Despite the lackluster pre-cancer screening results, Exact Sciences still appears to have decent chances of gaining FDA approval for Cologuard. The latest sell-off could present an attractive buying opportunity.

Finally, should the FDA approve Vascepa for patients with lower triglyceride levels than those for which the drug is currently approved, Amarin shares could take off. I think that all three of our horrendous stocks this week could be winners over the long run.