The pediatrician, however, is not always able to obtain an SPA or catheterized specimen and can only diagnose and treat based off a clean catch or bagged culture. Although there is no simple solution, the pediatrician needs to make the most informed decision possible.
A positive nitrite test significantly increases odds of a UTI, but the sensitivity is reported around 50%.20
Procalcitonin and C-reactive protein (CRP) also have been studied extensively in the diagnosis and management of UTI.21-26 A procalcitonin of >0.5 ng/mL was found to increase odds of UTI by a factor of more than 14.25 It also has been shown to have a sensitivity and specificity of 71% and 72%, respectively, for the diagnosis of acute pyelonephritis as well as 79% and 50%, respectively, for the presence of late renal scars.22
Procalcitonin performed better than CRP or white blood cell (WBC) counts. Further, procalcitonin testing may provide several additional benefits such as aiding the pediatrician in deciding what further imaging tests are necessary and which antibiotics to use.22 Procalcitonin also has been noted to better identify serious bacterial infections in the blood or nervous system compared with CRP.26
Whereas exact imaging choices in UTI have been debated significantly over the last 15 years, routine dimercaptosuccinic acid (DMSA) screening in UTI suffers a number of criticisms. First, the scans are not equally available across all geographic areas. Second, the scans are expensive, invasive, and they expose children to radiation with the primary outcome being close follow-up. In this scenario, an elevated procalcitonin might be considered in the future as a marker to more strongly consider DMSA scanning. It is also suggested that procalcitonin levels might be useful in determining whether intravenous or oral antibiotics are needed early in the infection.22 Currently an elevated CRP can be used as a marker of acute pyelonephritis in children without another source of infection even if the bacterial counts in the urine are low.20