A comparative study on bacterial cultures of urine samples obtained by clean-void technique versus urethral catheterization.
Contamination during urine collection causes difficulty in diagnosing infantile urinary tract infection (UTI). Though considered a gold-standard, suprapubic aspiration is traumatic and not always successful. Catheterization and clean void technique were often preferred but their relative usefulness has not been compared.


OBJECTIVE
To compare the culture results of clean void urine (CVU) and catheter urine (CathU) from children below 2-years old known to have no UTI. We tested whether the false-positive rates of CVU were significantly different from that of CathU.


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 10(3), 10(4) or 10(5)/mL. If mixed growth was believed to cause UTI, CathU produced less false-positive rates than CVU, though both rates were unacceptably high.


CONCLUSIONS
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.
Lau
Angela Yu
AY
Department of Paediatrics & Adolescent Medicine, Tuen Mun Hospital, Hong Kong.
Wong
Sik-Nin
SN
Yip
Kam-Tong
KT
Fong
Kwok-Wah
KW
Li
Samantha Po-Siu
SP
Que
Tak-Lun
TL
D002944:Circumcision, Male; D015169:Colony Count, Microbial; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D013048:Specimen Handling / Q000379:methods*; D014546:Urinary Catheterization; D014556:Urine / Q000382:microbiology*