\s=b\ Follow-up of children with recurrent urinary infections would be simplified by an accurate home-testing program for detection of infection. We provided nitrite test strips to the parents of 30 girls with recurrent urinary infection to determine if twice weekly home testing of first-voided urine could reliably detect infection. Infections were documented by dip slides or colony counts indicating more than 105 bacteria per milliliter of urine. Twenty-four families (80%) complied over a mean study period of 11 months, detecting 28 of 30 episodes of bacteriuria (93%). No false-positive tests occurred. Urinary nitrate, the substrate for nitrite production by bacteria, was universally present (> 100 \g=m\g/ml) in 80 children. The nitrite test is useful for home follow-up observation of children at high risk of bacteriuria if applied repeatedly by motivated parents.(Am J Dis Child 132: [46][47][48] 1978) Urinary infection in childhood is marked by its tendencies to occur in asymptomatic form and to recur following appropriate treat¬ ment.1 Consequently, elaborate pro¬ grams for culturing urine have been adopted to ascertain initial and recur¬ rent infections. In our hospital, for instance, children with recurrent uri¬ nary infections have been observed at six to 12-week intervals, with inter¬ views, urinalysis, urine culture, and colony counts. Such a program is expensive (exceeding $50 per visit) and inconvenient for the child and family. If a simpler, less expensive (Dr Scheifele). technique could be used by parents at home to detect recurrent infection, the cost and inconvenience of followup visits would be minimized. Parents have previously been shown to be capable of performing quite sophisti¬ cated home tests for infection.' ' In several recent surveys5"' the nitrite test (which detects a bacterial metab¬ olite in urine) detected 88% to 100% of urinary infections. We therefore ex¬ amined the accuracy of this simple, rapid test when performed by parents at home over a prolonged period.
METHODS The Nitrite TestThe nitrite test used is a commercially prepared dip strip (Bac-U-Dip, Warner/ Chilcott) costing 26 cents per test. In contact with 5 ftg/ml or more of nitrite, the reagent area turns from tan to pink or red in five minutes or less. Patients were instructed to wet the strip by holding it briefly in the first-voided morning urinary stream. No vulvar cleansing was per¬ formed. We found that storage of the strips in an amber vial at 4 C resulted in no loss of potency over a period of nine months.Urinary Nitrate Excretion A prerequisite for the success of the dip strip is the presence of the substrate for bacterial nitrate reducíase (nitrate) in the urine. To test for the presence of nitrate in urine, the qualitative method of Finnerty and Johnson* was used, employing diphenylamine-sulfuric acid solution. In the presence of 100 µg/ml or more of nitrate, a purple ring formed at the urine-reagent interface.Urine was obtained for nitrate testing from each study patient at each clinic visit. In addition, urin...