The NHS Commissioning Board has announced that it is widening its inquiry into hospitals with apparently worrying mortality rates.

On the day that Robert Francis QC issued his final report into the inquiry at Mid Staffordshire NHS Foundation Trust, the NHS CB announced that its medical director, Sir Bruce Keogh, would hold an investigation into five hospitals that were ‘outliers’ on one measure of hospital mortality, the Summary Hospital-Level Mortality Indicator.

Yesterday, the NHS CB said that Sir Bruce would also look at nine hospitals that are outliers on another measure, the older Hospital Standardised Mortality Ratio.

The hospitals now pulled into the inquiry are: North Cumbria University Hospitals NHS Trust; United Lincolnshire Hospitals NHS Trust; George Eliot Hospital NHS Trust; Buckinghamshire Healthcare NHS Trust; Northern Lincolnshire and Goole Hospitals NHS Foundation Trust; The Dudley Group NHS Foundation Trust; Sherwood Forest Hospitals NHS Foundation Trust; Medway NHS Foundation Trust; Burton Hospitals NHS Foundation Trust.

In a statement, Sir Bruce acknowledged that these trusts were already “working closely with a range of regulators” and sought to play down public concerns by saying that “if there were concerns that services were unsafe the regulators should have intervened.”

He said the purpose of his investigation was to make sure that patients, the public, politicians, and regulators all understood why the hospitals were showing up as outliers on the different measures.

The HSMR has been severely criticised both for the way that it is constructed and for the levels of variability that it can throw up. The first of Francis’ inquiries into Mid Staffs argued that a new measure was needed, and Sir Bruce set up a working group that led to the creation of the SHMI.

However, the methodology for the new measure, which is published by the NHS Information Centre, has yet to settle-down, and there are still questions about how useful it is in spotting quality problems at NHS trusts.

Sir Bruce has yet to announce the details and timescale for his investigation.