Is urine dipstick testing still useful in evaluating the presence of bacteriuria in a post antibiotic era?
BAUS ePoster online library. Taktak S. 06/26/19; 259497; P13-3
Mr. Samih Taktak
Mr. Samih Taktak
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Abstract
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INTRODUCTION

Urine-dipstick are widely used to evaluate the presence of bacteriuria. Previously reported reviews have suggested high levels of sensitivity and specificity. In a post antibiotic era, with increasing resistance patterns, we aim to re-evaluate the diagnostic accuracy across an entire hospital.

Method
Consecutive results of December 2017 paired urine dipstick tests and MSU received were evaluated. Significant bacteriuria was defined as single culture >10*5 cfu/ml. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for nitrites/leukocytes/combinations of them. Finally, the diagnostic accuracy was stratified according to resistance profiles.

RESULTS

1000 urine-dip and 1030 MSU results were analysed. Cohort results in Table 1. 57/237 MSU specimens were positive and 35/57 demonstrated resistance to either trimethoprim/nitrofurantoin/ciprofloxacin/amoxicillin.

22/45 specimens were resistant to trimethoprim. The sensitivity of the nitrite test for trimethoprim resistant bacteria was almost half that for trimethoprim sensitive bacteria. Resistance rates to other tested antibiotics was low. No differential effect was seen on sensitivity between antibiotic sensitive and resistant bacteria.

Conclusions
The presence of nitrites on urine dipstick analysis carries a much higher false negative rate than previously reported. Whilst previous reports had suggested that combining the results of nitrites and leucocytes can improve the combined sensitivity and specificity this was not found in our study. This false negative rate appears higher in trimethoprim resistant bacteria. Whilst many explanations could account for this our findings may suggest that continued antibiotic pressures and misuses may impact on the diagnostic accuracy of routinely available urine dip analysis.

INTRODUCTION

Urine-dipstick are widely used to evaluate the presence of bacteriuria. Previously reported reviews have suggested high levels of sensitivity and specificity. In a post antibiotic era, with increasing resistance patterns, we aim to re-evaluate the diagnostic accuracy across an entire hospital.

Method
Consecutive results of December 2017 paired urine dipstick tests and MSU received were evaluated. Significant bacteriuria was defined as single culture >10*5 cfu/ml. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for nitrites/leukocytes/combinations of them. Finally, the diagnostic accuracy was stratified according to resistance profiles.

RESULTS

1000 urine-dip and 1030 MSU results were analysed. Cohort results in Table 1. 57/237 MSU specimens were positive and 35/57 demonstrated resistance to either trimethoprim/nitrofurantoin/ciprofloxacin/amoxicillin.

22/45 specimens were resistant to trimethoprim. The sensitivity of the nitrite test for trimethoprim resistant bacteria was almost half that for trimethoprim sensitive bacteria. Resistance rates to other tested antibiotics was low. No differential effect was seen on sensitivity between antibiotic sensitive and resistant bacteria.

Conclusions
The presence of nitrites on urine dipstick analysis carries a much higher false negative rate than previously reported. Whilst previous reports had suggested that combining the results of nitrites and leucocytes can improve the combined sensitivity and specificity this was not found in our study. This false negative rate appears higher in trimethoprim resistant bacteria. Whilst many explanations could account for this our findings may suggest that continued antibiotic pressures and misuses may impact on the diagnostic accuracy of routinely available urine dip analysis.

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