Medical expert explains WHY Sheffield's case numbers are 'misleading'

Each day, a Public Health England dashboard gives the number of new confirmed coronavirus cases in each local authority area in England.

Sheffield has consistently been among the highest areas for confirmed cases and, at present, has the fourth highest number by local authority in the country.

But Dr Andrew Lee, a reader of global public health at Sheffield University and executive director of primary care and population health at NHS Vale of York clinical commissioning group, said the dashboard numbers were “misleading and alarming”.

This is because, he said, more people have been tested in Sheffield than in other areas.

Dr Lee said the data “does not measure all cases of disease, only what’s been reported or tested [...] If you test more, you will find more cases.

“In the case of Sheffield, put simply they’ve been testing a whole lot more so it’s not a surprise they’ve uncovered more of the iceberg.”

He also pointed out “everywhere is testing differently”, which makes comparisons difficult.

If areas are testing in different ways, for example, it is hard to directly compare their results, Dr Lee said.

Dr Lee said even if testing availability and methods were the same, it is still “tricky” to make comparisons as every area has “different demographic profiles”. For example, one area may have an older and more vulnerable population.

Greg Fell, director of Public Health in Sheffield, previously said the high number of confirmed cases in Sheffield does not mean there's more chance of being infected here than in other areas.

Dr Lee added: “Currently, confirmed cases are more likely to be patients with greater severity of illness that have ended up in hospital, so a lot of folk with milder infections out in the community won’t have been detected, diagnosed or reported.

“Also, if an area tests more of its healthworkers for the infection they are likely to find more cases as they are a higher risk group for infection (through frequent, prolonged exposure to ill infectious patients). So healthworkers are not reflective of the wider population.”

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