By Alisdair Stirling
The limits of dipstick testing to detect urinary tract infections have been exposed by a UK study which suggest even if blood, leucocytes and blood are negative 24% of women will still have a UTI.
The NHS funded study looked at 434 adult women with suspected lower UTI. The presence of bacteria was assessed and 66% had a confirmed infection.
The previously developed dipstick rule — based on presence of nitrite, or both leucocytes and blood — was moderately sensitive at 75%, but less specific – with a positive predictive value of 81% and a negative predictive value of 57%.
Varying the rule improved the predictive values. But even if all three dipstick variables were negative, 24% of women would be told they had no UTI when in fact they did.
Study leader Professor Paul Little, professor in primary care research at the University of Southampton School of Medicine said: ‘In practice this means clinicians should consider strategies such as delayed prescribing for such patients or alternatively advising a review consultation if symptoms are not settling..
British Journal of General Practice 2010; 60
Dipstick testing Tips on urine testing