Hospital bosses are carrying out a review of winter deaths after figures suggested there was a higher mortality rate at weekends.
Latest figures published by Mid Yorkshire Hospitals Trust show a statistical measure of deaths following emergency admission at weekends has increased by more than a third.
NHS organisations are required to have a Hospital Standardised Mortality Ratio (HSMR) - which uses complex calculations to work out the expected number of deaths - of 100.
Mid Yorkshire, which runs Pontefract, Pinderfields and Dewsbury hospitals, had a HSMR score of 129.29 for weekends in December, according to figures in a report to its last board meeting.
The weekend figure for the month was higher than the trust’s weekday HSMR of 92.51 in December, and had increased from 93.13 for weekends in August last year, trust board papers show.
Stephen Eames, Mid Yorkshire’s chief executive, said the trust was still within national targets for its HSMR score and the mortality rate was actually falling.
The raised HSMR for December was thought to be down to an increase in patients coming to hospital with respiratory problems.
Mr Eames said: “We are always going to see these little spikes.
“We are not concerned about it at all. What matters is if the spike continues over a period of time.
“We are not concerned about it but we need to understand if that’s the case.
“If the spike was to continue over a longer period of time that’s when I would start to say I’m concerned.”
NHS-wide research has shown that patients had a 16 per cent greater risk of death within 30 days if they were admitted to hospital at the weekend.
The government is moving towards a seven-day NHS service to make sure there are not fewer doctors and nurses on duty at the weekend.
Some NHS experts have questioned the reliability of HSMR data because it is a statistical measure and the only way of deciding if a death was avoidable is reviewing individual cases.
Mid Yorkshire Hospitals Trust was “highly commended” for reducing its mortality rates in 2013. The independent Dr Foster Hospital Guide said the trust’s overall HSMR score was 97, below the national average of 100 and down from 108 a year earlier. Mid Yorkshire was also improved weekend death rates among emergency patients , recording a HSMR score of 99.