This story was co-published with NPR's Shots blog.

Patients who suffer injuries, infections or mistakes during medical care rarely get an acknowledgment or apology, researchers at the Johns Hopkins University School of Medicine report.

The study was based on responses of 236 patients who completed ProPublica's Patient Harm Questionnaire during the one-year period ending in May 2013 and who agreed to share their data.

Results of the study, led by professor of surgery Marty Makary and conducted independently from ProPublica, were published online Nov. 13 by the Journal of Patient Safety. The study found:

It was common for health care providers to withhold information about medical mistakes. Only 9 percent of patients said the medical facility voluntarily disclosed the harm.

When officials did disclose harm it was often because they were forced to. Nine percent of respondents said the harm was only acknowledged under pressure.

Apologies were infrequent. Only 11 percent of patients or their family members reported getting an apology from a provider.

More than 30 percent reported paying bills related to the harm. The average cost: $14,024.

Another study last year in the Journal of Patient Safety estimated that at least 210,000 U.S. hospital patients a year die from medical mistakes. Yet while the problem is widespread, Makary and his research team wrote, there is little research into how patients feel about experiencing medical harm.

Clinicians may see the need to be more open with patients but lack the "moral courage" to do it, researchers said. Patient advocates and providers should work together on how to best inform patients, and medical schools and training programs can introduce the needed skills, they said.

The authors cautioned that because their findings are from a self-selected sample of patients it is not possible to draw definitive conclusions about patient harm or disclosure.

As of today, more than 600 people have volunteered to complete ProPublica's Patient Harm Questionnaire, including participants in the Consumers Union Safe Patient Project, which shared the survey.

The questionnaire helps ProPublica's reporters find stories and trends. Only respondents who first consented to participate were included in Makary's research.

Help us investigate patient safety: Patients who have been harmed, or their loved ones, are invited to complete our questionnaire. Researchers interested in the data can email reporter Marshall Allen at [email protected].