Urinary nitrite in symptomatic and asymptomatic urinary infection

• Published in: Archives of disease in childhood Vol. 62; no. 2; pp. 138 - 140
• Main Authors: Powell, H R, McCredie, D A, Ritchie, M A
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health 01.02.1987; BMJ; BMJ Publishing Group LTD
• Subjects: Adolescent; Bacterial diseases; Bacterial diseases of the urinary system; Biological and medical sciences; Child; Child, Preschool; E coli; Escherichia coli - isolation & purification; Follow-Up Studies; Human bacterial diseases; Humans; Infant; Infectious diseases; Inhalants; Medical sciences; Nitrites - urine; Time Factors; Urinary Tract Infections - diagnosis; Urinary Tract Infections - microbiology; Urinary Tract Infections - urine; Urine; Assay; Human; Infection; Screening; Urinary system disease; Nitrites; Urinary tract
• ISSN: 0003-9888; 1468-2044
• DOI: 10.1136/adc.62.2.138

The dipstrip test for urinary nitrite is fairly unreliable in symptomatic urinary infections and only 104 (52%) of 200 symptomatic children with urinary infection attending an emergency department had a positive result. The test yielded positive results, however, in 83 of 100 outpatients with largely asymptomatic urinary infection attending a follow up clinic because of known predisposition to urinary infection. This difference was highly significant. The finding of urinary nitrite is highly specific for urinary infection and only 1% of 300 uninfected urine specimens gave a positive result. After addition of a broth culture of Escherichia coli to sterile urine incubation at 37 degrees C for four to six hours was required before the nitrite test yielded positive results. This suggests that frequency of micturition in urinary infection reduces the reliability of the nitrite test. On the other hand, the use of overnight, first morning urine specimens may further improve the sensitivity. If nitrite testing is used for screening for urinary infection at home, however, patients should be warned not to rely on a negative result in the presence of symptoms of urinary infection.