Abstract
Urinary tract infections (UTIs) are common. The diagnosis is confirmed by urine culture which is costly and takes at least 24 hours before results are known. The aim of this study was to determine the diagnostic accuracy of dipstick test for the diagnosis of UTI in symptomatic adult patients. We conducted a cross-sectional study in the department of Infectious Diseases, Sousse-Tunisia during a two-year period. We included all patients with clinical signs of UTI. Urine samples were tested for the presence of leukocyte esterase (LE) and nitrites. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of LE and nitrites were calculated against urine culture as gold standard. Four hundred thirty one patients, 139 men (32%) and 292 women (68%) were included. One hundred sixty six patients (39%) had UTI. The most frequently isolated microorganism was Escherichia coli (75%). LE had a high sensitivity (87%) but a low specificity (64%), while nitrites had a high specificity (95%) but a low sensitivity (48%). Combined positive LE and nitrites had a high PPV (85%) and combined negative LE and nitrites had a high NPV (92%), while positive LE combined with negative nitrites had a low PPV (47%) and a low NPV (53%). In conclusion, in adult patients with UTI symptoms, an alternate diagnosis should be considered if the LE is negative, while an early empirical antibiotic therapy against Enterobacteriaceae should be started if the nitrites are positive.
Highlights
Urine samples were tested for the presence of leukocyte esterase (LE) activity and nitrites using dipstick test according to the manufacturer's instructions, and expire dates were checked before use
LE was more specific in men (78%) compared to women (45%), and the negative predictive value (NPV) of nitrites was higher in men (85%) compared to women (68%) (Table 2)
LE positivity combined with nitrites positivity had a positive predictive value (PPV) of 85%, LE negativity combined with nitrites negativity had a NPV of 92%, LE positivity combined with nitrites negativity had a PPV of 47% and LE negativity combined with nitrites positivity, noted in only 1.6% of patients, had a PPV of 86% (Table 3)
Summary
They occur in 60% of women at least once in their lifetime and account for 23% of hospitalacquired infections [1, 2]. Since urine culture is costly and takes at least 24 hours before results are known, the use of simpler and faster diagnostic methods such as dipstick test should be useful to guide the initial diagnosis especially in an emergency context. In 2015, the Société de Pathologie Infectieuse de Langue Française recommended dipstick test as a diagnostic method in UTIs for its high negative predictive value (NPV) in women and its high positive predictive value (PPV) in men. The aim of this study was to determine the diagnostic accuracy of dipstick test for the diagnosis of UTI in symptomatic adult patients [4]
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