This is part 8 of Health Care’s Colossus, a series about how UnitedHealth Group wields its unrivaled physician empire to boost its profits and expand its influence.

In every way, a study published this January in a major medical journal was a win for UnitedHealth Group. It showed that UnitedHealth’s preferred approach to covering Medicare patients, an especially profitable line of business, was producing higher-quality care for older Americans than the standard method.

But a closer inspection reveals reasons to distrust the narrative. The study was funded by UnitedHealth’s Optum subsidiary, co-authored by a top employee, and based in part on tightly controlled data from its own physician clinics. Its key finding seems to be a statistical mirage, due to flaws in its methodology, according to 13 independent experts who reviewed the manuscript for STAT.

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“It is not a valid comparison. It’s just two sets of data. The groups are so different,” said Gerard Anderson, a health policy professor and Medicare expert at Johns Hopkins University. He noted variations in patients’ locations, income levels, and use of health care services appear to have skewed the results. 

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