We expect UnitedHealth Group Inc. UNH to beat expectations when it reports first-quarter results on Apr 19, before market opens.Why a Likely Positive Surprise?Our proven model shows that UnitedHealth has the right combination of the two key ingredients to beat earnings estimates.Zacks ESP: Earnings ESP, which represents the difference between the Most Accurate estimate and the Zacks Consensus Estimate, is +0.58%. This is because the Most Accurate estimate of $1.73 is pegged higher than the Zacks Consensus Estimate of $1.72. The positive ESP is a meaningful indicator of a likely positive earnings surprise.Zacks Rank: UnitedHealth carries a Zacks Rank #3 (Hold). Note that stocks with a Zacks Rank of #1, 2 or 3 have a significantly higher chance of beating on earnings.The Sell-rated stocks (#4 or 5) should never be considered going into an earnings announcement. What is Driving the Better-Than-Expected Earnings?With a leading market presence across all private health insurance segments of North America and South America, UnitedHealth is poised to deliver better numbers in the to-be-reported quarter. Also, Medicare Advantage remains well positioned to increase the membership base to about 0.3 million and is on track to achieve 0.325–0.400 million members in net growth for 2016.Also, the strong performing Optum segment is likely to have driven the first-quarter top line and margin, supported by Medicaid and the International segment. The company’s well diversified portfolio continues to add to the upside.The positive trend is seen in the trailing four-quarter average surprise of +4.26%.However, the insurer is expected to have incurred losses from individual insurance business offered via public exchanges created under the Health Care Reform Act. For 2016, the insurer expects as much as $500 million in losses on the Obamacare plans.Other Stocks to ConsiderHere are three other stocks from the medical sector which you may want to consider as our model shows that they too have the right combination of elements to post an earnings beat this quarter: AbbVie Inc. ABBV with an Earnings ESP of +0.88% and a Zacks Rank #3. The company will release first-quarter earnings results on Apr 28.DaVita HealthCare Partners Inc. DVA with an Earnings ESP of +5.75% and a Zacks Rank #3 (Hold). The company is expected to release first-quarter earnings results on May 2. Humana Inc. HUM with an Earnings ESP of 0.55% and a Zacks Rank #3. The company is expected to release first-quarter earnings results on May 4.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report>>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report HUMANA INC NEW (HUM): Free Stock Analysis Report UNITEDHEALTH GP (UNH): Free Stock Analysis Report DAVITA HEALTHCR (DVA): Free Stock Analysis Report ABBVIE INC (ABBV): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research