The New Jersey Hospital Association, which supports reporting, opposes public release of that information.

"It may present an unfair picture of what is actually going on . . . when we have some hospitals that are not reporting and other hospitals that are reporting," said the hospital association's Holmes.

In Pennsylvania, the authority's 2007 annual report noted reporting disparities. For example, while one large academic medical center reported one serious event for every 200 days of patient care, a similar hospital reported one every 12,500 patient days.

A few hospitals, the authority noted, submitted no reports at all.

How many should be reported? James Conway, a quality expert at the Institute for Healthcare Improvement in Cambridge, Mass., said on average a review of 100 patient medical charts reveals 40 instances of harm.

"The best we have found anywhere is 20 instances of harm and the worst is over 100," Conway said. "Are all of those serious, reportable events? No, but it shows that even in the best hospitals, there is suffering and harm at a minimum, if not tragedy."

In the five years since the Pennsylvania law went into effect, the health department has cited four hospitals in Southeastern Pennsylvania for failing to report serious events.

None was fined.

Both states could impose a $1,000-a-day penalty for each failure to report.

The foreign objects left in the patients at Fox Chase and the severe-bedsore case at Abington are considered "never events."

Delinda Pendleton, Fox Chase's director of quality management, said in a statement that the patients were informed of the mistakes in face-to-face conversations. She said Fox Chase recognizes that reporting such errors provides opportunities "to learn and improve the already high quality of our patient care."

Yashima White, a spokeswoman for Mercy Fitzgerald, said in a statement that the hospital staff didn't realize that postoperative complications rose to the level of requiring a report. All three patients bled excessively after their release from the hospital, she said, and had to have additional surgery. The hospital has now adopted the health department's approach to ensure such problems are reported.

Besides Fox Chase, Mercy Fitzgerald and Abington, Brandywine Hospital in Chester County was cited for failing to file any serious-event reports from October 2006 through March 13, 2007.

Brandywine's chief executive, Mark A. Betz, said the hospital's failure to report happened when it was between risk-management directors. Steps have been taken to correct the lapse.

John J. Kelly, Abington's chief medical officer, said the hospital acted quickly in the case of the patient left on the bedpan. It implemented training sessions for nearly 1,000 nurses and spent $2.6 million to install 250 beds designed to reduce pressure ulcers.

That's how the system is supposed to work, and why reporting mistakes and trying to fix them are critical to improving patient care.

"We apologized to the patient and her family and have taken measures to prevent something like this from happening again," Kelly said. "We made a mistake. It was entirely avoidable."

But he also noted that the state, prompted by a complaint from the patient's family, began looking into the matter so quickly that the hospital hadn't had time to determine whether or not the incident had to be reported.

Still, the numbers suggest underreporting is more than just a passing problem.

Calvin Johnson, the Pennsylvania secretary of health, said only people with their "head in the sand" would fail to see the problem of uneven reporting by hospitals. But he noted that with about 200 hospitals and millions of patient visits each year, it is impossible for the state to check every chart.