Background: The early differentiation of upper urinary tract infection (UTI) from lower UTI in infants and children is essential, because renal parenchymal involvement in UTI has the greatest potential for causing irreversible renal damage. Commonly used inflammatory markers cannot be used reliably for such differentiation. Dimercaptosuccinic acid (DMSA) renal scintigraphy is the gold standard for the diagnosis of upper UTI (acute pyelonephritis); but it is expensive, not readily available in all centers and exposes the patients to radiation. There is a great need for a quick and accurate diagnosis test for renal involvement in UTI. Procalcitonin (PCT), a recently described marker of bacterial infection, has not been fully studied in relation to UTI in children.
Objectives: We conducted this research to study the ability of serum PCT to predict renal involvement in UTI (acute pyelonephritis) in comparison with the other commonly used inflammatory markers in these cases.
Methods: The serum PCT, C-reactive protein (CRP), total leukocytic count (TLC), band cells percent (BC%) and erythrocyte sedimentation rate (ESR) were studied in 25 children with UTI diagnosed by positive urine cultures and significant colony counts. They included 10 cases with acute pyelonephritis and 15 cases with lower UTI. Acute pyelonephritis was diagnosis by the presence of pyelonephritic changes in renal DMSA scans. Patients who received antibiotics within the previous week of admission or having extrarenal infection known to affect PCT level were excluded. Ten healthy children matched for age and sex served as a control group. A semiquantitative immunochromatographic rapid test (PCT-Q) was used for measurements of PCT.
Results: The mean values of serum PCT, CRP, TLC, BC% and ESR were significantly higher in patients with acute pyelonephritis than in those with lower UTI and controls (p ˂ 0.005). Serum PCT in upper UTI was mildly elevated in six cases (≥ 0.5-2 ng/mL), moderately elevated in three cases (˃ 2-10 ng/mL) and markedly elevated in one case (˃ 10 ng/mL). The mean of CRP was 54 ± 69 mg/L in cases with acute pyelonephritis versus 5.1 ± 2.9 mg/L in lower UTI (P = 0.004). The mean TLC was 15420 ± 4130 /mm³ in acute pyelonephritis compared to 10273 ± 2099 /mm³ in lower UTI (p = 0.000). Band cells had a mean value of 2.2 ± 1.8% in cases with acute pyelonephritis which was significantly elevated than the lower two groups (p = 0.001). Cases with lower UTI, had normal serum PCT and CRP levels, while mean values of TLC and ESR were significantly elevated versus controls (p = 0.001). Although BC% was higher in lower UTI compared to controls, this differences did not reach statistical significance. The sensitivity, specificity and predictive values of PCT for the detection of acute pyelonephritis were 100% each. All of CRP, TLC and ESR had sensitivity of 100% but a specificity of 93%, 87% and 40%, and positive predictive value of 91%, 83%, 53% respectively while negative predictive value was 100% for each of them.
Conclusions: Serum PCT is a valuable new infection marker with the highest sensitivity, specificity and predictive values for the detection of renal involvement in UTI compared to the other commonly used inflammatory markers in those cases. It allows early differentiation between acute pyelonephritisand lower UTI equal to dimercaptosuccinic acid (DMSA) renal scintigraphy.
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