By Richard Warry
BBC Health Editor, BBC News website
The two bodies use different methods to analyse standards
The fact that Dr Foster and the Care Quality Commission (CQC) appear to be drawing rather different conclusions about the state of the NHS would suggest that nobody really knows what is going on.
In fact, the differences are predictable because the two organisations do different things.
The CQC is the government's NHS inspectorate, which carries out a comprehensive monitoring programme of all NHS trusts.
Its rating system is based on a wide range of criteria, which includes patient safety and mortality rates, but also factors such as patient experience, access to services, efforts to improve public health and financial management.
Dr Foster is a private company which works closely with the government's NHS Information Centre in a so-called public-private joint venture to scrutinise the single issue of patient safety.
Even then, there are differences between the way the CQC and Dr Foster analyse this issue.
Both use comparable data on death rates - a measure known as hospital standardised mortality ratios (HSMRs) - which assesses whether the death rate at any given trust is above what could reasonably be expected, once the mix of patients' ages and severity of disease is taken into account.
However, Dr Foster has also developed other measures to feed into its analysis which are not used by the CQC.
These include whether a trust is feeding information on problems into the National Patient Safety Agency.
The first Dr Foster guide to healthcare was published in 2001. The idea was inspired by the experiences of the founder, Tim Kelsey, a former Sunday Times journalist whose wife gave birth in a hospital corridor.
The company hooked up with the NHS Information Centre in 2006, which at the time was searching for new ways to gather information about healthcare in the UK.
The CQC says making comparisons between its ratings and those of Dr Foster is spurious.
It says its annual health check is the "most comprehensive assessment of the NHS ever undertaken", although chair Baroness Young has admitted the system is in need of some reform.
Trusts must submit declarations on whether they think they are meeting the CQC standards in 44 areas, and they get penalised if inspectors decide the assessments are inaccurate after carrying out follow-up inspections of their own. These inspections take place at one in five trusts each year.
The CQC also uses survey information from patients and NHS staff, and from spot checks at every hospital.
In truth, the NHS is such a vast and complex monolith that no single monitoring body can get a completely accurate picture of everything that goes on, so the fact that two organisations such as the CQC and Dr Foster get a chance to crunch the data in different ways can only be a healthy thing.