HSJ analysis has identified the NHS providers whose patients are suffering increasing levels of avoidable harm, bucking a national trend of continuous month-on-month improvement.

Nationally, the proportion of patients suffering “new harms” fell by more than a quarter between April and December.

Providers reported that since the introduction of the NHS Safety Thermometer the proportion of patients suffering harm while under their care fell from 4.6 to 3.3 per cent. It has occurred in the face of rising demand for services, winter pressures and an ongoing squeeze on trust finances.

The tool, which trusts are paid to use under the commissioning for quality and innovation system, measures standards of care by counting incidence of “avoidable harms”. These include falls, pressure ulcers and venous thromboembolism.

The safety thermometer is intended to help trusts save money by reducing the amount of harm caused to NHS patients. It was developed under the “safe care” stream of the Department for Health’s quality, innovation, productivity and prevention programme.

HSJ’s analysis compared providers’ performances in December with that in their first month of credible data. Most trusts began submitting data in April 2012, although some began later. In situations where a trust’s first monthly figure was a major outlier in the context of the rest of its reports − as was frequently the case − HSJ counted from its second month of results.

Despite the general improvement, five trusts reported that over 3 per cent more patients were suffering from “new harms” in December, compared with the beginning of 2012-13.

The organisation with the biggest reported drop in performance was Hillingdon Hospitals Foundation Trust, the only foundation trust among the five. The provider reported 9 per cent of patients suffered new harms in December, compared with 3.6 per cent in July - the trust’s first month of reporting. All of the decline occurred between November and December.

A Hillingdon spokeswoman said the trust had identified a “data quality issue” relating to December, and had introduced “more robust monitoring” of data and more training for staff.

Two orthopaedic hospitals reported increases in new harms: the Royal National Orthopaedic Hospital Trust, with an increase of 3.1 percentage points, and the Royal Orthopaedic Hospital Foundation Trust, which reported a 2.5 point rise.

Many of the trusts with the highest rate of “new harms” have other existing financial and performance problems. These include Barnet and Chase Farm Hospitals Trust, which was at or below the national average level until December, when its level of harms increased, and Maidstone and Tunbridge Wells Trust.

However, HSJ’s analysis found no direct correlation between performance on avoidable harms and either the size of the trust or the scale of its cost improvement plan.

The most improved providers included Weston Area Health Trust, which has a turnover of just £95m, privately run Hinchingbrooke Health Care Trust and Peterborough and Stamford Hospitals Foundation Trust, which is grappling with unaffordable private finance initiative fees.

While there was no overall drop in quality at the end of 2012, 94 out of 201 trusts reported a decline in performance between November and December. This suggests winter pressures had an impact on the quality of care.

Despite that widespread drop in performance, some of the providers with comparatively poor figures for December disputed the validity of their data for that period. Wye Valley Trust, which saw the third steepest decline in performance across the year, put the difference down to a “coding error”.

Meanwhile, Maidstone and Tunbridge Wells admitted it needed to improve performance on falls and pressure ulcers, and said an improvement plan was in place. However, a spokeswoman added that it implemented the reporting system in stages, meaning its data could not be accurately compared to other trusts.

Foundation Trust Network chief executive Chris Hopson said: “I would encourage the minority of trust boards where performance is not improving consistently to analyse their data carefully, act swiftly to address the causes of any safety issues and learn from good practice elsewhere.”

But he said the thermometer should not be used to compare trusts because variations can occur due to patient mix and “differences in data collection”.