A comparative study on bacterial cultures of urine samples obtained by clean-void technique versus urethral catheterization

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Abstract

Methods

Paired CVU and CathU samples were collected from asymptomatic children admitted for micturiting cystourethrogram, and tested for leucocytes and nitrite, and bacterial culture using standard laboratory methods.

Results

Culture results for 98 children (82 boys, 16 girls; aged 6 ± 4.3 months) were analysed. Analysis by presence/absence of growths showed good agreement between CVU and CathU for boys (Kappa 0.42) but poor for girls (Kappa 0.18). When analysed by colony counts, agreement was poor with CVU yielding more counts than CathU (Kappa 0.1 for boys and 0.04 for girls). If all mixed growth results were considered as contaminants, the false positive rates for CathU and CVU were similar whether the cut-off was defined as 103, 104 or 105/mL. If mixed growth was believed to cause UTI, CathU produced less false-positive rates than CVU, though both rates were unacceptably high.

Conclusion

In uncircumcized boys, both CVU and CathU were prone to contamination. Though the contaminating bacterial counts were lower in CathU culture, the false-positive rates were high with the lower cut-off CFUs. Contrary to previous recommendations, CathU should be interpreted similar to CVU to avoid false positive diagnosis of UTI.

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