On receipt of written informed consent from the parents, the
children were randomized with a block size of 4 by an external
statistician to receive 5 mL/kg, up to 300 mL per day of either
cranberry juice or placebo juice in 1 or 2 daily doses for
6 months. Each center received sealed envelopes for randomization
purposes before the beginning of the recruitment phase,
so that the clinicians were unaware of the allocation of individual
patients. The parents completed a questionnaire providing
background data, nutritional status, and a medical history, and
were requested not to give the children any other Vaccinium
(eg, cranberry, blueberry, lingonberry) products during the
trial. The children were followed up for 1 year, during which
consumption of the juice and daily symptoms compatible with
UTI were recorded in a diary kept by the parents. The 1-year
follow-up period was chosen on the basis of our earlier experience
in a trial among adult women [11]. The parents were advised to
take the child to their own family physician whenever a fever or
local symptoms suggestive of UTI occurred. When UTI was diagnosed,
it was treated with a standard antimicrobial therapy
regimen, while the child continued taking the juice. If the child
had $3 UTI recurrences during the trial, antimicrobial prophylaxis
for 6 months was recommended. The physicians were
asked to record their diagnosis and the resulting treatment on
a follow-up sheet, which was returned to the center concerned at
the last visit. The results of all urine tests carried out during the
follow-up were collected from the laboratory databases.
Compliance with the protocol was determined on the basis of
the self-report sheets and by counting the empty juice cartridges
returned by the parents at the end of the trial.