Anthem (NYSE:ANTM) will be reporting fourth-quarter 2015 earnings this Wednesday. While the quarter was important, it's really only a prelude for bigger things to come. So while the numbers will be useful to know, what's more key is to see how Anthem is executing on its major potential growth drivers. Here are the three most important questions investors should seek answers to.

What can we glean about exchange enrollment trends?
The Affordable Care Act's 2016 open enrollment period ends Jan. 31, so Anthem won't have complete Obamacare data, since enrollment won't be finished by the time Anthem reports its Q4 earnings. When industry leader UnitedHealth Group (NYSE:UNH) reported earnings last week, executives shared their exchange enrollment as of the end of 2015 and gave some estimates for total 2016 enrollment based on the trends they'd observed thus far. You can probably expect something similar from Anthem, which has a big exchange footprint and is actively looking to grow it despite the dual headwinds of lowered expectations for overall exchange enrollment this year and a pricing environment Anthem has struggled with.

Unlike UnitedHealth Group and Aetna (NYSE:AET), Anthem's exchange enrollment has been profitable. We'll want to keep an eye on how profitable, of course -- Anthem's margins in this space have usually run in the low to mid-single digits -- but that's loads better than UnitedHealth Group's estimated 15% to 16% loss on exchange enrollment. Also, given that UnitedHealth Group has signaled that it may leave the ACA exchanges in 2017 and that Aetna plans to reduce its footprint from 17 states to 15, it'll be important to hear what Anthem management thinks about the exchanges as a long-term growth opportunity for the company.

How about those star ratings?
With 10,000 baby boomers expected to retire daily through 2029, Medicare Advantage looks poised to grow nicely as Anthem, UnitedHealth Group, and Aetna actively market their plans to these new customers. The Centers for Medicare & Medicaid Services give each Medicare Advantage a rating of one to five stars based on a number of different factors that all measure plan quality. It's a useful way to show consumers what plans are likely to be the best experience for them as they increasingly rely on healthcare in retirement.

Anthem's major problem is that it's way behind Aetna and UnitedHealth Group in its plan quality. Aetna has 87% of its members in plans rated four stars or higher; UnitedHealth Group reports that it expects 63% of its members to be in a plan rated four stars or higher in 2016, with plans to grow to 80% in 2018. Anthem trails at roughly 25% of membership in four-star or higher plans. Now, management is working extensively to grow that number -- and as investors, we'll want to hear progress on that improvement.

What news on the Cigna acquisition?
The $54 billion Cigna (NYSE:CI) acquisition will be a hot topic of conversation. The deal is expected to close in second half 2016, and 99% of shareholders on both sides support the merger. Two looming questions remain: Will it happen, and will it happen on time? With antitrust regulators circling this deal and with Aetna's proposed Humana buyout, keep your ears open for anything about antitrust concerns -- and also whether Anthem plans to keep to its previously guided timeline.

Anthem's plans for Medicare Advantage growth are closely tied to the Cigna acquisition, as the hope is to grow Anthem's commercial insurance footprint and then convert those workers to Anthem Medicare advantage plans as they age. That represents an opportunity to get the first bite at the apple before competing Medicare Advantage providers swoop in and try to poach these members. And if Anthem can get these folks locked into a plan before someone else does, then status quo bias, or the tendency of people not to change something once they've begun, could play right into Anthem's plans.

Pay attention
As I've previously written, 2016 looks likely to be more of a "building" year for Anthem than necessarily a blockbuster earnings growth year. And this call will help us get a feel for just how Anthem is planning to execute on its core drivers, which will hopefully help propel the business in the coming several years.

Michael Douglass has no position in any stocks mentioned. The Motley Fool recommends Anthem and UnitedHealth Group. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.