Determining the feasibility of randomising infants, children and young people to invasive and non-invasive urine sampling techniques

Background

Obtaining uncontaminated urine samples from children can be difficult. Clean catch urine (CCU) is non-invasive but may be slow and lead to a contaminated sample, whereas transurethral bladder catheterisation (TUBC) and suprapubic aspiration (SPA) are invasive. We assessed the feasibility of randomising children to a definitive trial.

Methods

FROG was a multicentre, randomised feasibility trial with a mixed-methods perspectives study, health-economic analysis and stakeholder consensus meeting. Children under 16 years requiring urine testing for suspected urinary tract infection (UTI) who could not provide a midstream sample were eligible for the feasibility trial. Parents, children and healthcare professionals were eligible for the perspectives study and consensus meeting.

Results

Of 703 children screened, 170 were offered the study and 99 were recruited. Overall, 64/170 (37.6%) consented to randomisation, exceeding the feasibility threshold (33%); 32 were allocated to CCU and 32 to TUBC. The allocated method was received by 46/64 (71.9%); delays, unsuccessful collection and distress contributed to non-receipt. Among participants with available cultures, contamination occurred in 2/12 (16.7%) allocated CCU and 0/6 allocated TUBC. No participants consented to randomisation involving SPA.

The perspectives study included 14 parent interviews, 89 parent questionnaires and 28 staff across 5 focus groups and 1 interview. CCU and TUBC were considered acceptable, although participants balanced speed and accuracy against pain and distress. SPA availability and acceptability were limited. A total of 19 stakeholders attended the consensus meeting; 94% supported recruiting children aged under 18 months and 100% supported comparing CCU with TUBC, without SPA. Accuracy was the highest-ranked outcome.

Conclusions

A definitive trial comparing CCU-first with TUBC-first in children aged under 18 months is feasible. Its primary outcomes should reflect diagnostic accuracy and clinical consequences of contamination, with successful collection, collection time, pain and distress assessed as key secondary outcomes.

Plain English Summary

Urinary tract infections are common in children, but accurate diagnosis depends on obtaining a reliable sample of urine. During collection, bacteria from the skin or surrounding area can get into the sample. This is called contamination and can make it appear that an infection is present when it is not. This mistake may lead to extra tests, delays in making treatment decisions and the unnecessary use of antibiotics.

Internationally, three methods are used to collect urine from young children, and we do not know which method is best. A “clean catch” sample involves catching urine in a sterile container. It does not hurt, but collection can be slow and contamination of the sample is not unusual. A catheter sample uses a tube passed into the child’s bladder, while a third method uses a needle passed into the bladder through the skin. Catheter and needle sampling may provide cleaner samples more quickly but can cause pain or distress.

We examined whether families would join a study comparing these three methods and whether a larger trial would be practical and acceptable. We screened 703 children and offered the study to 170 families. Overall, 99 families took part and 64 agreed that their child could be randomly allocated to clean catch or catheter sampling, which was more than we expected. No family agreed to randomisation involving needle sampling. A total of 46 of the 64 (71.9%) children received their allocated method. Delay, unsuccessful collection and distress contributed to others receiving a different method. Among children with available laboratory results, 2 of 12 clean catch cultures were contaminated compared with none of 6 catheter cultures.

We spoke with 14 parents and 28 healthcare professionals, and collected data from 89 parent questionnaires to gather their views about the study. They told us that both clean catch and catheter sampling were acceptable, but participants balanced accuracy (obtaining a reliable sample) and speed against the pain and distress. A meeting of 19 parents and professionals supported the proposal to do a larger study to compare clean catch with catheter sampling in children aged under 18 months attending emergency departments. Accuracy was considered the most important outcome.

This shows that a larger trial is feasible. It should assess diagnostic accuracy and whether contamination leads to further healthcare contacts, repeat sampling or antibiotics. Successful collection, collection time, pain and distress should also be measured.