GPs do not need to test blood glucose in patients with stable diabetes every six months, as recommended by NICE, as it leads to a high rate of false positives an NHS report has concluded.
Annual monitoring would give more meaningful information on changes to HbA1c which for most people happen quite slowly, the NHS Diabetes report said.
Statistical modelling showed for patients whose HbA1c is currently 56mmol/mol, six-monthly monitoring would pick up 405 positive tests per 1,000 patients – that is HbAlc readings above 58.5 mmol/mol - but 28% of those would be due to measurement variation and not a real increase.
For the same group of patients annual monitoring would pick up 479 per 1,000 patients but with only 16% would be false positives, the University of Oxford researchers who did the analysis found.
In other groups with lower starting HbA1c readings most of the positive tests seen with six-monthly tests would be false positives, the report said.
For someone with a starting HbA1c, a positive test six months later has a 64% chance of being false compared with 31% after a year, the figures showed.
‘For many people with diabetes, six-monthly monitoring is more likely to yield a false-positive test – attributable to the within-measurement variability of HbA1c – than a true-positive test, attributable to the change over time in glycaemic control,’ the researchers concluded.
‘Annual monitoring gives more time for a meaningful change to occur in HbA1c.’
The team added that high rates of false-positive tests mean prescribing decisions, such as a dose increase or an additional medication, being made the basis of a ‘chance finding rather than a true change’.
Professor Roger Gadsby, a GP and associate clinical professor at Warwick Medical School said he agreed with the conclusions of the report.
He said: ‘It provides new evidence that an annual HBA1c measurement is adequatefor people who are stable. I am sure NICE will take notice of this report when it publishes its updated guidance on type 2 diabetes which is being worked on at present.’
He said that anyone who had a change in treatment - either up-titration of dose or new medication - would need more frequent monitoring.
Dr Colin Kenny, a GP in County Down and committee member of the Primary Care Diabetes Society said he believed annual monitoring of stable patients to be a pragmatic solution with rising numbers of patients and that it fitted with the QOF.
He said: ‘There is a lot of sense in it and that it is a reasonable approach but I think people are fixated on six-months.’
A NICE spokesperson said the guidance on the management of type 2 diabetes was currently in the process of being updated and all available evidence will be considered.
He said: ‘Until the update is published, healthcare professionals should continue to follow the recommendations set out in the current guideline.’