UEL professor casts doubt over Lyme disease study showing three-fold increase

A tick before and after feeding. Picture: UEL

A tick before and after feeding. Picture: UEL - Credit: Archant

A university professor has dismissed figures appearing to show Lyme disease cases increasing in the UK.

Professor Sally Cutler from UEL. Picture: UEL

Professor Sally Cutler from UEL. Picture: UEL - Credit: Archant

Sally Cutler, professor of medical microbiology at the University of East London, questioned the study in the journal BMJ Open which suggested the infection may be three times more common than current estimates.

She said the report - Incidence of Lyme disease in the UK - includes "suspected" or "possible" cases meaning the numbers were likely to be overestimated.

Prof Cutler said: "This might cause alarm. This study reports a different way to calculate the number of cases."

The study includes three categories of patients: clinically diagnosed; treated suspect cases with a positive diagnostic test; and treated possible cases.

Ixodes ricinus. Picture: UEL

Ixodes ricinus. Picture: UEL - Credit: Archant

"Including patients who were only 'suspect' and 'possible of Lyme disease cases' will result in an over-estimation of cases," Prof Cutler said.

Past rates are based on officially reported cases of the tick-borne infection that are counted after positive blood tests, she added.

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The report's researchers looked at a database of 8.4 million patient records, covering about 8 per cent of the population.

Among these, 4,083 cases of Lyme disease were detected between 2001 and 2012 with a steep rise from 60 in 2001 to 595 in 2012.

Applying this to the wider population suggested to researchers there were more than 7,738 cases across the country in 2012, higher than the usual estimate of 2,000 to 3,000 annual cases.

Dr Victoria Cairns, the report's co-author, said the possibility of overestimating and underestimating the number of cases was discussed in the study.

"Overall, we took a conservative approach to identifying cases. Cases that were diagnosed in hospital or specialist clinics are not counted, so the true total could be higher," she said.

She added the study is unique in that it includes estimates of case numbers based on the whole pattern of data on GP diagnoses of the disease.

"It is true our results differ from previous estimates. Those other studies will have been based on rigorous criteria and were carefully designed, but they were very limited, often to laboratory test results only," Dr Cairns said.

Lyme disease is spread via bites from infected ticks. Symptoms can include a circular red rash though this is not always the case.

Visit the NHS website for more information.