UnitedHealth posted a better-than-expected fourth-quarter profit, but a nagging rise in medical costs and care utilization surprised Wall Street.

UnitedHealth Group Inc. reported fourth-quarter profit that surpassed Wall Street’s expectations in its first financial statement since a top executive was killed in New York last month.

UnitedHealth reported a full-year medical cost ratio — the percentage of premiums spent on medical care — of 85.5%, compared with the average analyst estimate of 84.96%, according to data compiled by LSEG. On an adjusted basis, the company earned $6.81 per share in the fourth quarter, compared with estimates of $6.72 per share.

UnitedHealth Group beat estimates for fourth quarter profit as the Eden Prairie-based health care giant released its first earnings report since the fatal ambush last month of top executive Brian Thompson in New York City.

UnitedHealth Group reported a fourth-quarter profit on Thursday that beat analysts' estimates as the healthcare conglomerate spent less on covering members' medical costs. On an adjusted basis, the company earned $6.