A SUPERBUG outbreak originally thought to have killed 18 people may have been responsible for 28 deaths, according to an independent expert.

Ten people who died at the Vale of Leven Hospital during the clostridium difficile (C. diff) outbreak between January 2007 and June 2008 did not have the bacteria listed on their death certificates, despite medical records suggesting it was a contributing factor.

The research was carried out by infectious disease expert, Professor George Griffin, who gave evidence to the Vale of Leven Hospital Inquiry this week.

Official inquiry figures say 55 patients were affected by C. diff during the outbreak and 18 died.

But Griffin, of University of London St George's College, uncovered a further 10 potential victims from a group of 31 who died at the hospital or after discharge.

He reviewed case reports of the 31 patients, all of whom had C. diff and were put in isolation areas with other C. diff-positive patients.

His review revealed that 10 of the patients who died with C. diff as a cause or contributing factor did not have the bacteria mentioned on part one or part two of their death certificates.

UK death certificates include a two-part cause of death section. Part one refers to the direct cause while part two records anything else contributory.

Griffin said: "If C. diff is not recorded on a death certificate and those records are used for subsequent studies or to give annual reports, then it is likely there will be considerable under-reporting.

"Death certification is a very important role of a doctor's professional life. It is very important for the family, first of all, to know what their loved one has died of.

"Secondly, it is very important from medico-legal purposes, should there be any suspicion that death has not been due to natural causes, then that must be recorded."

Despite Griffin's findings, the inquiry team does not believe it is necessary to broaden its remit or contact the families of the other 10 patients in whose deaths Griffin believes C. diff played a part.

A spokesman said: "There's no requirement for the inquiry to broaden its remit – its terms of reference were broad enough to allow the inquiry to investigate the cases of a wider group of patients than the figure of 18 originally mentioned.

"Essentially, the inquiry is doing the job it was set up to carry out and, as a result, there are no plans to contact additional families."

The inquiry's terms of reference include a clause to "establish what lessons can be learned and to make recommendations" about C. diff management in a report to be prepared by September 2012.

This week, a ward was closed at after seven patients tested positive for C. diff this month.

Some of the victims of the Vale of Leven outbreak are represented by Patrick McGuire, a partner at Thompsons Solicitors.

He said the families and survivors hope the lessons learned from the inquiry will help prevent further fatal outbreaks and added that Griffin's findings would be upsetting to the victims. McGuire said: "This evidence must be very distressing for the families involved. It is becoming increasingly clear that there were shortcomings at the Vale of Leven and we are confident the inquiry will reveal these problems in detail.

"We have heard of staffing problems and failures in planning and procedure.

"Lessons must be learned and applied to make lasting changes to infection control, not just at the Vale of Leven, but across Scotland.

The inquiry, before Lord MacLean at Maryhill Community Central Halls, continues.