Patient safety is a critically important topic for health care journalists. Yet collecting the data needed to report on it thoroughly can be frustratingly difficult.

For a new report, former journalist Michael L. Millenson (@MLMillenson), explains the challenges he and his colleagues encountered collecting the data they needed to produce a nonpartisan report, “The Politics of Patient Harm: Medical Error and the Safest Congressional Districts.” The first analysis of patient safety by congressional district, the report ranks each district as good, fair or poor on patient safety.

Early in his career, Millenson covered health care for The Chicago Tribune. He is the author of “Demanding Medical Excellence: Doctors and Accountability in the Information Age,” and president of Health Quality Advisors LLC.

For this patient safety report, he found that – even in the best districts – at least one person dies needlessly every day and eight patients are harmed. The report also shows that 14 more individuals die and 105 are injured every month in hospitals in districts rated “poor” on safety than in those rated “good.”

In poor districts, preventable medical errors cause an average of 553 deaths and 4,148 injuries annually. In fair districts the average annual rate was 469 deaths and 3,518 injuries and in good districts, the rate was 385 deaths and 2,888 injuries.

In a new “How I did it” article, Millenson explains the challenges of collecting and reporting the data needed to compare one congressional district against others.

“In health care, cooking up answers to what look like simple questions can quickly get complicated,” he writes. Surprisingly, it was difficult just to determine how to define the term “hospital” because there are so many different types of hospitals. Just distinguishing a local hospital’s performance from that of another hospital miles away was challenging because multiple hospitals owned by one system may share a provider billing number, he explains.

For journalists, this report and Millenson’s explanation of how it was compiled is useful for comparing patient safety scores in one district versus others, and it’s useful as a way to keep the issue of patient safety in the public eye 15 years after the publication of the Institute of Medicine’s landmark report on the subject, “To Err is Human: Building a Safer Health System.”