The Relationship between Group B Streptococcus Infection in the Vagina with C-Reactive Protein and Procalcitonin Levels in Pregnant Women with Preterm Premature Rupture of Membranes

Background: Preterm premature rupture of membranes (PPROM) is a significant obstetric complication, contributing to increased maternal and neonatal morbidity and mortality. Group B Streptococcus (GBS) infection is a key factor associated with PPROM, inducing inflammation and weakening of the fetal membranes. C-reactive protein (CRP) and procalcitonin are biomarkers of inflammation that may aid in early detection of GBS infection in pregnant women with PPROM.

Methods: A cross-sectional study was conducted involving 64 pregnant women with PPROM treated at Prof. Dr. I.G.N.G. Ngoerah General Hospital, Denpasar, from March 2023 to May 2024. Vaginal and rectal swabs were cultured to identify GBS. Serum CRP and procalcitonin levels were measured. Pearson correlation and chi-square tests were used to analyze the relationship between GBS infection and these biomarkers.

Results: The prevalence of GBS infection among participants was 50%. CRP levels were significantly higher in GBS-positive cases (mean 7.88 mg/L) compared to GBS-negative cases (mean 3.43 mg/L; p = 0.038), with a strong positive correlation (r = 0.824). Procalcitonin levels were also elevated in GBS-positive cases (mean 0.066 ng/mL) vs. GBS-negative cases (mean 0.031 ng/mL; p = 0.044), showing a moderate positive correlation (r = 0.567). Sensitivity and specificity were 80% and 76.5% for CRP and 75% and 69.5% for procalcitonin, respectively. CRP demonstrated a prevalence ratio (PR) of 4.16, indicating a stronger association with GBS infection compared to procalcitonin (PR 3.08).

Conclusion: Both CRP and procalcitonin are valuable markers for diagnosing GBS infection in pregnant women with PPROM. CRP exhibits stronger diagnostic performance and is recommended as the primary biomarker. Procalcitonin serves as a complementary tool, enhancing the diagnostic process. These findings underscore the importance of integrating these markers into clinical practice to improve maternal and neonatal outcomes.

Introduction

Preterm premature rupture of membranes (PPROM) is defined as the rupture of the chorioamniotic membranes before the onset of labor and before 37 weeks of gestation. PPROM is a significant concern in obstetrics due to its association with increased maternal and perinatal morbidity and mortality. While the exact etiology remains unclear, it is thought to involve multiple factors and mechanisms, including reproductive tract infections. The detection of pathogenic microorganisms in the vagina following membrane rupture supports the hypothesis that bacterial infections play a role in its pathogenesis [1], [2].

Approximately 150,000 of the 560,000 annual preterm births in the United States are caused by PPROM, accounting for 40%–50% of all preterm deliveries [3]. In Indonesia, data from Prof. Dr. I.G.N.G. Ngoerah General Hospital between July 2015 and June 2016 reported that 14.5% of PPROM cases occurred before 37 weeks of gestation [4]. Group B Streptococcus (GBS) colonization in the maternal vagina has been identified as a significant factor associated with PPROM. Studies report positive GBS cultures in 17% of preterm PPROM cases compared to 5% in term pregnancies [5].

GBS, a Gram-positive bacterium found in the lower gastrointestinal tract and vagina, colonizes approximately 10%–30% of pregnant women as commensals. Ascending GBS infections can cause an inflammatory response in the uterus, leading to the production of prostaglandins by the membranes, contributing to membrane rupture [6]. Gold-standard diagnosis of GBS infection involves culture-based analysis from vaginal and rectal swabs. However, simpler and more accessible hematological tests, such as C-reactive protein (CRP) and procalcitonin, have been proposed as alternative markers for identifying inflammation and infection [7], [8].

Elevated CRP and procalcitonin levels have been associated with maternal and fetal infections in cases of PPROM. CRP, synthesized by hepatocytes in response to tissue injury and inflammation, has been widely used as a systemic inflammatory marker. Procalcitonin, a prohormone released in response to bacterial endotoxins and pro-inflammatory mediators, shows potential for predicting infection severity [9]. Recent studies have demonstrated significant correlations between elevated CRP and procalcitonin levels and intra-amniotic infections, including chorioamnionitis, among PPROM patients [10], [11].

Given the potential of these markers in predicting GBS infection in PPROM, this study aims to evaluate the relationship between maternal serum CRP and procalcitonin levels and GBS infection in preterm pregnancies. Improved screening and diagnosis of GBS infection can lead to timely interventions, reducing maternal and perinatal complications [12].

Materials and Methods

Study Design

This study is an analytical study with a cross-sectional design aimed at determining the relationship between maternal C-reactive protein (CRP) and procalcitonin levels and group B Streptococcus (GBS) infection in pregnant women with preterm premature rupture of membranes (PPROM) treated at Prof. Dr. I.G.N.G. Ngoerah General Hospital, Denpasar, during 2023–2024. Data collection was conducted once for each sample.

Study Setting and Period

The study was conducted in the Obstetrics and Gynecology Department of Prof. Dr. I.G.N.G. Ngoerah General Hospital, Denpasar. The study period was from March 2023 to May 2024 or until the minimum sample size was met.

Population and Sample

• Target Population: All pregnant women with PPROM.

• Accessible Population: Pregnant women with PPROM treated at Prof. Dr. I.G.N.G. Ngoerah General Hospital from March 2023 to May 2024.

• Sampling Technique: Consecutive sampling was used, including all eligible PPROM cases until the required sample size was met.

Inclusion Criteria

1. Pregnant women diagnosed with PPROM through clinical history, physical examination, and supporting tests.

2. Maternal age ≥ 18 years.

3. Gestational age < 37 weeks.

4. Willing to participate as evidenced by signed informed consent.

Exclusion Criteria

1. Other inflammatory or infectious conditions unrelated to PPROM that may affect CRP and procalcitonin levels, such as acute infections and sepsis.

2. Non-Indonesian citizens.

Sample Size Calculation

The minimum sample size was calculated using Lemeshow’s formula, with an assumed GBS infection prevalence of 21.3%, a 95% confidence level (Zα = 1.96), and a margin of error (d) of 0.15. The calculation yielded a minimum sample size of 32, including a 10% adjustment for potential dropouts.

Data Collection

Data were collected from pregnant women with PPROM treated at the delivery ward of Prof. Dr. I.G.N.G. Ngoerah General Hospital.

1. Clinical and Laboratory Data:

• Vaginal and rectal swab cultures were performed to identify GBS infection.

• Blood samples were taken for CRP and procalcitonin level measurement.

2. Variables:

• Independent variable: GBS infection.

• Dependent variables: CRP and procalcitonin levels.

• Confounding variables: Maternal age, gestational age, parity, gravidity, history of PPROM, and history of preterm birth.

Procedure

1. Participants were placed in the lithotomy position for vaginal and rectal swab collection.

2. lood samples (3 mL) were collected from the cubital vein using aseptic techniques.

3. Laboratory analyses:

• swab cultures were incubated and identified using MacConkey and Blood Agar media followed by VITEK® 2 Compact for GBS detection.

• Serum CRP and procalcitonin levels were analyzed in the clinical pathology laboratory.

Data Analysis

Data were analyzed using SPSS version 21.

1. Descriptive Analysis: Frequency and percentage for categorical variables; mean/median for continuous variables.

2. Normality Test: Shapiro-Wilk for small samples (<50), Kolmogorov-Smirnov for larger samples (>50).

3. Bivariate Analysis:

• T-test or Mann-Whitney for comparing CRP and procalcitonin levels between groups with and without GBS infection.

• Chi-square test for associations between CRP, procalcitonin, and GBS infection.

• Correlation analysis to determine the strength of the relationship between variables (r > 1 indicates a strong correlation).

Results

Normality Test

The normality test using the Shapiro-Wilk method revealed that procalcitonin levels in the positive group were normally distributed (p = 0.199, p > 0.05), while in the negative group, the data were not normally distributed (p = 0.000, p < 0.05; see Table I). For CRP levels, the data were not normally distributed in both the positive and negative groups, with p-values of 0.003 and 0.008, respectively. Based on these results, CRP levels in both groups were analyzed using a non-parametric approach, specifically the Mann-Whitney U Test. The analysis showed a statistically significant difference in CRP levels between the positive and negative groups, with a p-value of 0.038 (p < 0.05). The higher mean rank in the positive group indicated that CRP levels were significantly elevated in pregnant women with PPROM and GBS infection compared to those without infection. These findings support the hypothesis that CRP levels can serve as a useful marker for identifying GBS infection in PPROM cases.

Table I. Characteristic Normality Test Results

	P value shapiro wilk group (p < 0.05)		Mean ± Sum rank mann-whitney		Mean rank T-test		P value mann-whitney (p < 0.05)	P value T-test (p < 0.05)
	Positive(n = 32)	Negative (n = 32)	Positive (n = 32)	Negative (n = 32)	Positive (n = 32)	Positive (n = 32)
C-reactive protein (mg/L)	0.003 *	0.008 *	47.20 ± 1510.50	17.80 ± 569.50			0.038***
Procalsitonin (ng/mL)	0.199	<0.001**			0.06603 0.03130			0.044***

For procalcitonin levels, further analysis was conducted using an independent t-test, as the data in the positive group were normally distributed. The t-test results revealed a statistically significant difference in procalcitonin levels between the positive and negative groups, with a p-value of 0.044 (p < 0.05). The mean procalcitonin level in the positive group was 0.06603 ng/mL, significantly higher than the mean level in the negative group, which was 0.03130 ng/mL. The mean difference was 0.034734 ng/mL, with a 95% confidence interval ranging from 0.022384 to 0.047085, indicating a credible and consistent difference. These results support the hypothesis that procalcitonin levels are higher in pregnant women with PPROM and GBS infection. The significant difference observed, regardless of variance assumptions, highlights procalcitonin as a relevant and reliable inflammatory marker for diagnosing GBS infection in PPROM cases.

In conclusion, the statistical analyses demonstrated that both CRP and procalcitonin levels were significantly elevated in pregnant women with PPROM and GBS infection compared to those without infection. These findings indicate that CRP and procalcitonin can serve as valuable diagnostic markers for GBS infection in PPROM cases, with procalcitonin showing particular promise as an additional inflammatory marker in clinical settings.

Distribution of Characteristics: Age, Gravida, Gestational Age, History of PPROM, and Preterm Birth in Group B Streptococcus Infection

Table II presents the demographic and clinical characteristics of two patient groups: those with positive results (n = 32) and those with negative results (n = 32). The mean age of patients in the positive group was 28.94 years, with a standard deviation of 56.254, while the mean age in the negative group was 26.69 years, with a standard deviation of 6.214. The mean gestational age in the positive group was 29.66 weeks, with a standard deviation of 3.756, compared to 29.69 weeks, with a standard deviation of 3.693 in the negative group.

Table II. Sample Characteristics Distribution Table

Variable	Group
	Positive (n = 32)	Negative (n = 32)
Age	28.94 ± 56.254	26.69 ± 6.214
Gestational Age	29.66 ± 3.756	29.69 ± 3.693
Gravida
- Primigravida	21 (65.63%)	17 (53.13%)
- Multigravida	11 (34.38%)	15 (46.88%)
History of Premature Rupture of Membranes
- Yes	9 (28.13%)	12 (37.50%)
- No	23 (71.88%)	20 (62.50%)
History of Preterm Birth
- Yes	9 (28.13%)	10 (31.25%)
- No	23 (71.88%)	22 (68.75%)
C-reactive protein (mg/L)	7.8781 ± 1.752	3.4291 ± 1.401
Procalcitonin (ng/mL)	0.066 ± 0.0257	0.031 ± 0.0236

In terms of gravida status, the positive group included 21 primigravida patients (65.63%) and 11 multigravida patients (34.38%), while the negative group included 17 primigravida patients (53.13%) and 15 multigravida patients (46.88%). A history of previous PPROM was reported in 9 patients (28.13%) in the positive group and 12 patients (37.50%) in the negative group, while 23 patients (71.88%) in the positive group and 20 patients (62.50%) in the negative group had no prior history of PPROM. Regarding a history of preterm birth, 9 patients (28.13%) in the positive group and 10 patients (31.25%) in the negative group had such a history, while 23 patients (71.88%) in the positive group and 22 patients (68.75%) in the negative group had no history of preterm birth.

As shown in Fig. 1, the distribution of CRP and procalcitonin levels varies between GBS-positive and GBS-negative groups. For laboratory parameters, the mean CRP level in the positive group was 7.8781 mg/L, with a standard deviation of 1.752, while the mean CRP level in the negative group was 3.4291 mg/L, with a standard deviation of 1.401. The mean procalcitonin level in the positive group was 0.066 ng/mL, with a standard deviation of 0.0257, compared to 0.031 ng/mL, with a standard deviation of 0.0236 in the negative group. The positive group tended to have higher CRP and procalcitonin levels, which may indicate a more severe inflammatory or infectious condition.

Fig. 1. Flowchart of the procedure.

Other variables, such as age, gravida, history of PPROM, and history of preterm birth, showed differences that may provide additional insights into the characteristics of each group. Further statistical analysis will be required to determine the significance of these differences and their implications for understanding the relationship between these variables and Group B Streptococcus infection.

Bivariate Analysis of Correlation Between CRP and Procalcitonin

The correlation analysis presented in Table III shows a significant relationship between Group B Streptococcus (GBS) infection and both CRP and procalcitonin levels. A Pearson correlation coefficient of 0.824 indicates a strong positive correlation between GBS infection and CRP levels, with a p-value of 0.038 (p < 0.05), demonstrating that the relationship is statistically significant. This suggests that CRP levels tend to increase in the presence of GBS infection, supporting the use of CRP as an indicator for GBS infection in pregnant women with preterm premature rupture of membranes (PPROM).

Table III. Results of Pearson Analysis of CRP Variables and Procalsitonin

Variabel	R Pearson Value	P Value
C-Reactive Protein	0.824	<0.001
Procalsitonin	0.567	<0.001

Additionally, a Pearson correlation coefficient of 0.567 indicates a moderate positive correlation between GBS infection and procalcitonin levels, with a p-value of 0.044 (p < 0.05), which is also statistically significant. This finding suggests that procalcitonin levels may increase with GBS infection, though the effect is less pronounced compared to CRP.

In conclusion, these results support the hypothesis that there is a significant relationship between CRP and procalcitonin levels and GBS infection in pregnant women with PPROM. CRP shows a stronger association with GBS infection than procalcitonin, making it a more effective marker for identifying GBS infection. However, procalcitonin can serve as a complementary marker in the diagnostic process. The clinical implications of these findings suggest that CRP could be prioritized as a primary indicator for GBS infection, while procalcitonin adds value as an additional diagnostic tool.

Chi-Square Analysis of C-Reactive Protein and Procalcitonin

The Chi-Square test results in Tables IV and V reveal a significant relationship between GBS infection and the levels of both CRP and procalcitonin. For the relationship between GBS infection and CRP levels, the Pearson Chi-Square test, based on 64 valid cases, yielded a p-value of 0.038 (p < 0.05), indicating a statistically significant association. Furthermore, the Prevalence Rate (PR) of 4.16 suggests that individuals with GBS infection have a 4.16 times higher likelihood of elevated CRP levels compared to those without the infection.

Table IV. Results of C-Reactive Protein Chi Square Analysis

	C-Reactive Protein		P Value	PR
	Increased	Not increased
GBS infection (+)	24 (75.0%)	8 (25.0%)	0.038	4.16
GBS infection (−)	6 (18.8%)	26 (81.2%)

Table V. Results of Chi Square Analysis of Procalcitonin

	Procalcitonin		P Value	PR
	Increased	Not increased
GBS infection (+)	21 (65.6%)	11 (34.4%)	0.044	3.09
GBS infection (−)	7 (21.9%)	25 (78.1%)

Similarly, for the relationship between GBS infection and procalcitonin levels, the Pearson Chi-Square test, also based on 64 valid cases, produced a p-value of 0.044 (p < 0.05), confirming a statistically significant association. The PR of 3.09 indicates that individuals with GBS infection are 3.09 times more likely to have elevated procalcitonin levels compared to those without the infection.

Both CRP and procalcitonin have proven to be effective inflammatory markers for detecting GBS infection in pregnant women with preterm premature rupture of membranes (PPROM). However, CRP demonstrated a stronger association with GBS infection, as evidenced by higher correlation values and Chi-Square test results. Among GBS-positive cases, 75.0% of pregnant women exhibited elevated CRP levels, compared to only 18.8% among GBS-negative cases. For procalcitonin, 65.6% of GBS-positive cases showed elevated levels, compared to 21.9% in GBS-negative cases.

In terms of diagnostic performance, CRP showed slightly higher sensitivity (80%) than procalcitonin (75%) for detecting GBS infection. Moreover, CRP had higher specificity (76.5%) compared to procalcitonin (69.5%) in ruling out GBS infection. These findings underscore CRP's superiority as a predictive and diagnostic marker for GBS infection, particularly in distinguishing between infected and non-infected cases.

In conclusion, CRP emerges as a more effective inflammatory marker for detecting GBS infection in pregnant women with PPROM due to its stronger statistical association and superior diagnostic performance. However, procalcitonin remains a valuable complementary marker, providing additional diagnostic confidence in identifying GBS infection. Both markers can be integrated into clinical practice to enhance the accuracy of GBS infection diagnosis in this high-risk population.

Discussion

Preterm premature rupture of membranes (PPROM) is a significant obstetric condition, often complicated by infections such as Group B Streptococcus (GBS). This study highlights the utility of inflammatory markers such as C-reactive protein (CRP) and procalcitonin in predicting GBS infections among pregnant women with PPROM.

The average maternal age in this study was 28.94 years in the GBS-positive group and 26.69 years in the GBS-negative group, with no significant difference (p = 0.477). These findings align with studies from Prof. Dr. R. D. Kandou Manado, Indonesia, which reported that most PPROM cases occur in women aged 20–35 years, a common reproductive age range. Similar observations have been made in India, where PPROM predominantly affects women aged 20–30 years, correlating with higher pregnancy rates in this demographic. The GBS-positive rate of 37% observed in this study also aligns with global reports indicating that GBS colonization is a major contributor to PPROM prevalence. These results emphasize the importance of targeted interventions in this reproductive age group [13].

Regarding gravida status, primigravida women comprised 65.6% of the GBS-positive group and 53.13% of the GBS-negative group, with no significant difference (p = 0.794). This finding corroborates other studies indicating a higher prevalence of PPROM in primigravida women, where cervical incompetence and infections such as GBS are key contributing factors [14]. The link between infections and PPROM has been well-documented, with studies highlighting a 19% incidence of premature rupture of membranes in association with bacterial infections [15].

The gestational age at the time of PPROM was predominantly preterm, with averages of 29.66 weeks in the GBS-positive group and 29.69 weeks in the GBS-negative group (p = 0.626). These findings align with reports that PPROM occurs in 3%–18% of preterm pregnancies, with a higher prevalence in preterm compared to term gestations [16]. This underscores the critical need for early detection of infections to manage complications associated with PPROM effectively.

Significant differences in CRP and procalcitonin levels were observed between the GBS-positive and GBS-negative groups. The mean CRP levels were significantly higher in the GBS-positive group (7.8781 mg/L) than in the GBS-negative group (3.4291 mg/L, p = 0.038). These results align with findings by Suwardewa et al., who demonstrated that maternal CRP levels were significantly elevated in GBS-positive cases, supporting CRP as a reliable marker for detecting bacterial infections in PPROM [17]. Similarly, the mean procalcitonin levels were significantly higher in the GBS-positive group (0.066 ng/mL) than in the GBS-negative group (0.031 ng/mL, p = 0.044). While procalcitonin is less sensitive than CRP, it remains a useful complementary marker for diagnosing GBS infections [18].

CRP demonstrated superior sensitivity (80%) and specificity (76.5%) compared to procalcitonin (sensitivity 75%, specificity 69.5%) in detecting GBS infections. This finding is consistent with previous studies indicating that CRP is more reliable than procalcitonin in predicting intra-amniotic infections and complications related to PPROM [19]. Procalcitonin’s moderate sensitivity and specificity make it a useful adjunct marker, particularly when combined with other biomarkers such as interleukin-6. The Pearson correlation coefficient for CRP (0.824) indicates a strong positive relationship with GBS infection, while the coefficient for procalcitonin (0.567) reflects a moderate correlation [20]. These results reaffirm CRP’s stronger association with GBS infections, making it a more effective marker for early detection and clinical management [21].

This study’s findings emphasize the clinical utility of combining CRP and procalcitonin as part of a diagnostic panel for GBS infections in PPROM. The integration of these markers into routine clinical practice could enhance the early detection of infections, thereby reducing maternal and neonatal complications associated with PPROM. Future research should explore the combined diagnostic performance of CRP, procalcitonin, and other inflammatory markers, such as IL-6, to optimize diagnostic accuracy and improve outcomes in high-risk pregnancies [22].

Conclusion

This study concludes that both CRP and procalcitonin are effective biomarkers for detecting GBS infections in pregnant women with PPROM, with CRP showing a stronger diagnostic value due to its higher sensitivity (80%), specificity (76.5%), and prevalence ratio (4.16) compared to procalcitonin (sensitivity 75%, specificity 69.5%, prevalence ratio 3.08), indicating that CRP is a more reliable marker for identifying GBS infections, supporting its use as a primary biomarker in clinical practice to improve maternal and neonatal outcomes.