Annual microalbuminuria testing ‘reveals many false positives’

By Lilian Anekwe

Annual urine testing for microalbuminuria produces a high number of false positives that render it ‘almost unusable', according to a study by primary care researchers.

NICE guidance recommends GPs should test patients with type 1 diabetes once a year for microalbuminuria, but the results of urine albumin tests can vary widely from day to day within the same patient.

Researchers at the University of Oxford argued this could lead to patients with normal urine albumin level testing positive for microalbuminuria and receiving inappropriate treatment.

They used the annual urine albumin test results of 483 patients aged 5 to 25 years old with type 1 diabetes, and fitted them to a statistical model to look for trends and variation in albumin creatinine ratio, to estimate rates of positive tests and false positives.

The number of false positive fell if patients were screened less frequently than recommended by NICE. (see box)

Using the estimates, in patients who are screened annually in accordance to NICE guidance ‘there would be approximately one false positive test for every one true positive test over the first five years.'

'There would also be approximately one false negative test for every two true positive tests,' researchers concluded.

Dr Jason Oke, a statistician at the University of Oxford department of primary healthcare, said: ‘The high number of false-positives – people measuring above thresholds who usually have normal albuminuria – suggests that urine albumin monitoring based on NICE guidance in people with type 1 diabetes fails to target treatment appropriately.'

Dr Oke told delegates at the South West Society for Academic Primary Care conference in Oxford: ‘The test is almost unusable because it's so variable.'

Dr Rafael Perera, who also worked on the study said: ‘With blood pressure we know you need to standardise measurements because they are so variable. So it may be that standardisation is needed for this.'