HES data is of low quality and is unreliable (citation 1,citation 2, citation 3, citation 4, citation 5)
"Concerns remain about the quality of HES data. The overall percentage of admissions with missing or invalid data on age, sex, admission method, or dates of admission or discharge was 2.4% in 2003. For the remaining admissions, 47.9% in 1996 and 41.6% in 2003 had no secondary diagnosis recorded (41.9% and 37.1%, respectively, if day cases are excluded). In contrast to some of the clinical databases, if no information on comorbidity is recorded, we cannot tell whether there is no comorbidity present or if comorbidity has not been recorded. Despite these deficiencies, our predictive models are still good. In the most recent report of the Society of Cardiothoracic Surgeons, 30% of records had missing EuroSCORE variables. Within the Association of Coloproctology database, 39% of patients had missing data for the risk factors included in their final model. A comparison of numbers of vascular procedures recorded within HES and the national vascular database found four times as many cases recorded within HES."
and this from a letter by authors including Bruce Keogh:
"This latest study raises more concerns about hospital episode statistics data, showing that errors are not consistent across the country."
and this from Royal College of Physicians,as recently as 2012:
"This change is necessary because the current process for the collection of data for central returns that feed HES, and the content of the dataset itself, are both no longer appropriate for the widening purposes for which HES are used. "
I can find little to support Brian Jarman's stance claiming that HES data is accurate and reliable. Prof Jarman's study relies massively on HES data, as it is this very data from which his HSMRs are calculated. It would be fascinating if Prof Jarman could produce some published evidence to support his stance on HES data. If the UK data is less complete than the US data, it could well lead to a massive difference in HSMRs that is nothing to do with care standards, but that is purely down to data quality. The HSMR is another part all in itself.