We found three important results in this study which investigated serum procalcitonin levels in pregnant women with ASB. The first one: Serum procalcitonin levels are significantly higher in pregnant women with ASB than the control group. The second one is: Recurrent ASB and urinary tract infection risk are higher in pregnant women with positive procalcitonin levels at the time of first diagnosis of ASB. This result revealed that high procalcitonin level might be a risk factor for subsequent complications in pregnant women with ASB and the third result of the study is procalcitonin level was normal despite the higher levels of WBC, ESR and CRP levels in the control group. These results supported that serum procalcitonin is a reliable marker for either diagnoses or exclusion of urinary tract infection in pregnant women.
ASB is the most common type of urinary tract infection in pregnancy and found in 4-7% of pregnancies[5]. Pregnancy may cause anatomical, physiological and hormonal changes in women and these changes can increase the frequency of ASB[6]. Presence of ASB in a pregnant woman represents a significant health risk. The most important risk is development of acute and chronic pyelonephritis in pregnant women with ASB. It is known that pyelonephritis can develop in 15-50% of pregnant women if ASB is not treated[7]. Many complications can be prevented with early treatment of ASB during pregnancy. In this respect, studies for early diagnosis and treatment of ASB during pregnancy are very important.
It is accepted that, routine screening of pregnant women for ASB, should be done in the first visit and at regular intervals during pregnancy for early diagnosis and treatment but some authors suggest the screening of ASB in regions with high prevalance[8, 9]. Our region is not a high prevalence area for ASB so most of patients were in the second trimester in our study. Urine culture is still the screening method for ASB. However it takes time, a second sample for culture is necessary for definitive diagnosis and it does not predict recurrences.
Serum procalcitonin is a new marker in pregnant women population. There was no significant difference of serum procalcitonin levels between pregnant women and healthy controls[8, 10, 11]. Procalcitonin levels do not change with pregnancy-related conditions (type of birth, time of birth, type of anesthesia and the stress of childbirth), but are affected by premature rupture of membranes and infectious conditions, such as group B streptococcal colonization[12]. Montagnana et al. showed that serum procalcitonin was associated with preeclampsia[13]. Following this study, Can et al. found that there was a significant correlation between severe preeclampsia and procalcitonin levels[5]. Another study published recently showed that serum procalcitonin, CRP and D-dimer was significantly associated with preeclampsia[14].
To our knowledge, this is the first study in the literature investigating serum procalcitonin levels in pregnant women with ASB; thus, normal limit of serum procalcitonin levels in pregnant women with ASB is not established yet. Our study showed that 30% of the patient with ASB had high procalcitonin levels and all patients in the control group had negative procalcitonin assays. We calculated the sensitivity and specificity of procalcitonin assay for ASB as 30% and 100%, respectively furthermore, positive predictive value was 100% and the negative predictive value was 65%. Therefore we suggest that procalcitonin may be used in conjunction with urine culture in ASB diagnosis and follow up.
Serum procalcitonin level has still been studied in urinary tract infections and a significant correlation between the grade 3 vesico-urethral reflux and procalcitonin was shown in the children. In the same study, serum procalcitonin levels which were higher than 0, 5 ng/ml were associated with an increased risk of recurrent urinary tract infection[15]. Consistent with this study, we found significant recurrence rate in ASB patients with elevated procaltionin levels. In our study 44% of ASB patients had recurrence following the 2 months of the treatment of ASB and all of them had elevated procalcitonin levels. In another study among 1-13 months old babies, serum procalcitonin levels predicted acute pyelonephritis complicated with renal scar with 83% sensitivity and 94% specificity[16]. In our study, none of the women experienced systemic infection or sepsis and we don’t have fetal outcome data.
Other studies were performed investigating the predictive value of serum procalcitonin levels in urinary tract infections of children, but there was limited number of studies about pregnant women especially with urinary tract infections.
In our study, positive of serum assay was detected in 30% of pregnant women with ASB, and 4 of these 9 patients (44%) developed recurrent urinary tract infections after two months of treatment. This result supported that positive serum procalcitonin assay could be a predictive marker of recurrent urinary tract infections in the ASB population.
For the other parameters for infections: White blood cell count is usually normal in pregnancy, but the number of neutrophils can increase. There might be a significant leucocytosis increased up to 25.000 / mm3 during labor and puerperium. Also serum alkaline phosphatase can increase and may associate with inflammation[17]. In our study, leucocytosis was not seen in pregnant women as in controls. ESR starts to increase after 10 th weeks of gestation. The increase is moderate and it returns to normal level at 1 month after labor[18]. CRP levels were shown to be significantly higher in healthy pregnant women during the first 4 weeks of gestation[19]. In our study, CRP and ESR levels were above normal, but there was no significantly difference between the control and ASB group. But none of the healthy pregnant women had elevated procalcitonin levels and there was significant elevation of procalcitonin in the ASB group. This result showed that serum procalcitonin assay might be more reliable inflammatory marker than ESR, WBC and CRP in pregnant women with ASB.