Rapid testing for group B streptococcus during labour: a test accuracy study with evaluation of acceptability and cost-effectiveness

Benefits and harms of antenatal and newborn screening programmes in health economic assessments: the VALENTIA systematic review and qualitative investigation

Background

Health economic assessments are used to determine whether the resources needed to generate net benefit from an antenatal or newborn screening programme, driven by multiple benefits and harms, are justifiable. It is not known what benefits and harms have been adopted by economic evaluations assessing these programmes and whether they omit benefits and harms considered important to relevant stakeholders.

Objectives

(1) To identify the benefits and harms adopted by health economic assessments in this area, and to assess how they have been measured and valued; (2) to identify attributes or relevance to stakeholders that ought to be considered in future economic assessments; and (3) to make recommendations about the benefits and harms that should be considered by these studies.

Design

Mixed methods combining systematic review and qualitative work.

Systematic review methods

We searched the published and grey literature from January 2000 to January 2021 using all major electronic databases. Economic evaluations of an antenatal or newborn screening programme in one or more Organisation for Economic Co-operation and Development countries were considered eligible. Reporting quality was assessed using the Consolidated Health Economic Evaluation Reporting Standards checklist. We identified benefits and harms using an integrative descriptive analysis and constructed a thematic framework.

Qualitative methods

We conducted a meta-ethnography of the existing literature on newborn screening experiences, a secondary analysis of existing individual interviews related to antenatal or newborn screening or living with screened-for conditions, and a thematic analysis of primary data collected with stakeholders about their experiences with screening.

Results

The literature searches identified 52,244 articles and reports, and 336 unique studies were included. Thematic framework resulted in seven themes: (1) diagnosis of screened for condition, (2) life-years and health status adjustments, (3) treatment, (4) long-term costs, (5) overdiagnosis, (6) pregnancy loss and (7) spillover effects on family members. Diagnosis of screened-for condition (115, 47.5%), life-years and health status adjustments (90, 37.2%) and treatment (88, 36.4%) accounted for most of the benefits and harms evaluating antenatal screening. The same themes accounted for most of the benefits and harms included in studies assessing newborn screening. Long-term costs, overdiagnosis and spillover effects tended to be ignored. The wide-reaching family implications of screening were considered important to stakeholders. We observed good overlap between the thematic framework and the qualitative evidence.

Limitations

Dual data extraction within the systematic literature review was not feasible due to the large number of studies included. It was difficult to recruit healthcare professionals in the stakeholder's interviews.

Conclusions

There is no consistency in the selection of benefits and harms used in health economic assessments in this area, suggesting that additional methods guidance is needed. Our proposed thematic framework can be used to guide the development of future health economic assessments evaluating antenatal and newborn screening programmes.

Study registration

This study is registered as PROSPERO CRD42020165236.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: NIHR127489) and is published in full in Health Technology Assessment; Vol. 28, No. 25. See the NIHR Funding and Awards website for further award information.

Association between intrapartum antibiotic prophylaxis for Group B Streptococcus colonization and clinical chorioamnionitis among patients undergoing induction of labor at term

BACKGROUND

Rectovaginal colonization with Group B Streptococcus during pregnancy has historically been shown to be associated with an increased risk of clinical chorioamnionitis and peripartum infectious morbidity.

OBJECTIVE

Newer observational data in the era of intrapartum antibiotic prophylaxis suggest a possible reversal of this association; however, it is unclear if this is related to differences in labor management for those with and without Group B Streptococcus colonization. We therefore sought to assess the association between intrapartum antibiotic prophylaxis for Group B Streptococcus colonization and clinical chorioamnionitis within the context of a randomized induction of labor trial with a standardized labor protocol.

STUDY DESIGN

We performed an exploratory secondary analysis of a randomized trial of patients undergoing term induction at a tertiary care center. Patients received third trimester Group B Streptococcus screening and intrapartum antibiotic prophylaxis as routine care. Group B Streptococcus detection was performed using a carrot broth-enhanced subculture to Group B Streptococcus Detect approach (Hardy Diagnostics, Santa Maria, CA). Labor management was protocolized per the trial. Patients with unknown Group B Streptococcus status or who did not receive intrapartum antibiotic prophylaxis, if indicated, were excluded. The primary outcome was diagnosis of clinical chorioamnionitis, compared between patients who received intrapartum antibiotic prophylaxis for known Group B Streptococcus positive status (by culture, history, or Group B Streptococcus bacteriuria) and those who were Group B Streptococcus negative and did not receive intrapartum antibiotic prophylaxis. Secondary outcomes included postpartum endometritis, wound infection, a composite maternal peripartum infectious morbidity, and neonatal outcomes.

RESULTS

A total of 491 patients were enrolled in the trial. Of these, 466 had a known Group B Streptococcus status and received or did not receive intrapartum antibiotic prophylaxis accordingly and were included in this analysis: 292 (62.7%) were Group B Streptococcus negative and did not receive intrapartum antibiotic prophylaxis, and 174 (37.3%) were Group B Streptococcus positive and received intrapartum antibiotic prophylaxis. The majority of patients were Non-Hispanic Black (78.1%) and nulliparous (59.7%). There were no differences in demographic, clinical, induction or labor characteristics between groups. Patients who were Group B Streptococcus positive had a 49% lower rate of clinical chorioamnionitis (8.1% vs 14.7%, odds ratio, 0.51; P=.03) and a lower rate of peripartum infectious morbidity (8.1% vs 15.8%, odds ratio, 0.47; P=.02) compared to those who were Group B Streptococcus negative. Infants born to patients who were Group B Streptococcus positive were significantly less likely to be admitted to the neonatal intensive care unit (3.4% vs 15.1%, P<.001).

CONCLUSION

Although Group B Streptococcus colonization has historically been considered a risk factor for clinical chorioamnionitis, in the era of universal antibiotic prophylaxis for Group B Streptococcus positive patients, our findings support the point that intrapartum antibiotic prophylaxis for Group B Streptococcus positivity is associated with lower rates of clinical chorioamnionitis and peripartum infectious morbidity among patients undergoing induction with protocolized labor management. These findings demonstrate that intrapartum antibiotic prophylaxis for Group B Streptococcus may protect against perinatal infectious morbidity, a phenomenon that warrants further investigation.

Women's knowledge of and attitudes towards group B streptococcus (GBS) testing in pregnancy: a qualitative study

BACKGROUND

20-25% pregnant women in the UK carry group B streptococcus (GBS) which, if left undetected, is transmitted from pregnant mothers to their babies during birth in 36% of cases. This transmission leads to early onset GBS infection (EOGBS) in 1% of babies which is a significant cause of mortality and morbidity in newborns. The literature available suggests women's knowledge of GBS is low, with many women unaware of the GBS bacterium. In addition, attitudes towards GBS testing have not been widely examined, with research mostly focusing on attitudes towards potential GBS vaccination.

AIM

To examine women's knowledge of GBS in pregnancy and their attitudes towards GBS testing.

METHODS

Semi-structured interviews with 19 women (5 pregnant and 14 postpartum). Interviews were transcribed and analysed using systematic thematic analysis.

RESULTS

Four main theme categories were identified. Participants had varying levels of awareness of GBS, with the information provided by health professionals not being clearly explained or the importance of GBS being downplayed. Participants wanted more information and to feel informed. Overall, the majority had positive attitudes towards being offered and taking up GBS testing, and this study identified some of the key factors influencing their decision. These included: seeing GBS testing as just another routine procedure during pregnancy; that it would lower the risk of their baby becoming unwell; provide reassurance; and allow them to prepare; and provide informed choices. Participants also expressed a few common concerns about GBS testing: questioning the invasiveness of the procedure; risks to themselves and the baby; and the risk of receiving antibiotics.

CONCLUSIONS

Women need clear, detailed information about GBS and GBS testing, and women's concerns are important to address if routine GBS testing is implemented. The efficacy of implementing routine universal testing in the UK is currently being investigated in a large multi-centre clinical trial; the GBS3trial, further qualitative research is needed to look at the acceptability of different methods of GBS testing, as well as the acceptability of GBS testing to women in specific groups, such as those planning a home birth or those from different ethnic backgrounds.

A rapid intrapartum test for group B Streptococcus to reduce antibiotic usage in mothers with risk factors: the GBS2 cluster RCT

BACKGROUND

Mother-to-baby transmission of group B Streptococcus (Streptococcus agalactiae) is the main cause of early-onset infection.

OBJECTIVES

We investigated if intrapartum antibiotic prophylaxis directed by a rapid intrapartum test reduces maternal and neonatal antibiotic use, compared with usual care (i.e. risk factor-directed antibiotics), among women with risk factors for vertical group B Streptococcus transmission, and examined the accuracy and cost-effectiveness of the rapid test.

DESIGN

An unblinded cluster randomised controlled trial with a nested test accuracy study, an economic evaluation and a microbiology substudy.

SETTING

UK maternity units were randomised to either a strategy of rapid test or usual care.

PARTICIPANTS

Vaginal and rectal swabs were taken from women with risk factors for vertical group B Streptococcus transmission in established term labour. The accuracy of the GeneXpert^® Dx IV GBS rapid testing system (Cepheid, Maurens-Scopont, France) was compared with the standard of selective enrichment culture in diagnosing maternal group B Streptococcus colonisation.

MAIN OUTCOME MEASURES

Primary outcomes were rates of intrapartum antibiotic prophylaxis administered to prevent early-onset group B Streptococcus infection and accuracy estimates of the rapid test. Secondary outcomes were maternal antibiotics for any indication, neonatal antibiotic exposure, maternal antibiotic duration, neonatal group B Streptococcus colonisation, maternal and neonatal antibiotic resistance, neonatal morbidity and mortality, and cost-effectiveness of the strategies.

RESULTS

Twenty-two maternity units were randomised and 20 were recruited. A total of 722 mothers (749 babies) participated in rapid test units and 906 mothers (951 babies) participated in usual-care units. There were no differences in the rates of intrapartum antibiotic prophylaxis for preventing early-onset group B Streptococcus infection in the rapid test units (41%, 297/716) compared with the usual-care units (36%, 328/906) (risk ratio 1.16, 95% confidence interval 0.83 to 1.64). There were no differences between the groups in intrapartum antibiotic administration for any indication (risk ratio 0.99, 95% confidence interval 0.81 to 1.21). Babies born in the rapid test units were 29% less likely to receive antibiotics (risk ratio 0.71, 95% confidence interval 0.54 to 0.95) than those born in usual-care units. The sensitivity and specificity of the rapid test were 86% (95% confidence interval 81% to 91%) and 89% (95% confidence interval 85% to 92%), respectively. In 14% of women (99/710), the rapid test was invalid or the machine failed to provide a result. In the economic analysis, the rapid test was shown to be both less effective and more costly and, therefore, dominated by usual care. Sensitivity analysis indicated potential lower costs for the rapid test strategy when neonatal costs were included. No serious adverse events were reported.

CONCLUSIONS

The Group B Streptococcus 2 (GBS2) trial found no evidence that the rapid test reduces the rates of intrapartum antibiotic prophylaxis administered to prevent early-onset group B Streptococcus infection. The rapid test has the potential to reduce neonatal exposure to antibiotics, but economically is dominated by usual care. The accuracy of the test is within acceptable limits.

FUTURE WORK

The role of routine testing for prevention of neonatal infection requires evaluation in a randomised controlled trial.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN74746075.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 12. See the NIHR Journals Library website for further project information.

Rapid intrapartum test for maternal group B streptococcal colonisation and its effect on antibiotic use in labouring women with risk factors for early-onset neonatal infection (GBS2): cluster randomised trial with nested test accuracy study

BACKGROUND

Mother-to-baby transmission of group B Streptococcus (GBS) is the main cause of early-onset infection. We evaluated whether, in women with clinical risk factors for early neonatal infection, the use of point-of-care rapid intrapartum test to detect maternal GBS colonisation reduces maternal antibiotic exposure compared with usual care, where antibiotics are administered due to those risk factors. We assessed the accuracy of the rapid test in diagnosing maternal GBS colonisation, against the reference standard of selective enrichment culture.

METHODS

We undertook a parallel-group cluster randomised trial, with nested test accuracy study and microbiological sub-study. UK maternity units were randomised to a strategy of rapid test (GeneXpert GBS system, Cepheid) or usual care. Within units assigned to rapid testing, vaginal-rectal swabs were taken from women with risk factors for vertical GBS transmission in established term labour. The trial primary outcome was the proportion of women receiving intrapartum antibiotics to prevent neonatal early-onset GBS infection. The accuracy of the rapid test was compared against the standard of selective enrichment culture in diagnosing maternal GBS colonisation. Antibiotic resistance profiles were determined in paired maternal and infant samples.

RESULTS

Twenty-two maternity units were randomised and 20 were recruited. A total of 722 mothers (749 babies) participated in rapid test units; 906 mothers (951 babies) were in usual care units. There was no evidence of a difference in the rates of intrapartum antibiotic prophylaxis (relative risk 1.16, 95% CI 0.83 to 1.64) between the rapid test (41%, 297/716) and usual care (36%, 328/906) units. No serious adverse events were reported. The sensitivity and specificity measures of the rapid test were 86% (95% CI 81 to 91%) and 89% (95% CI 85 to 92%), respectively. Babies born to mothers who carried antibiotic-resistant Escherichia coli were more likely to be colonised with antibiotic-resistant strains than those born to mothers with antibiotic-susceptible E. coli.

CONCLUSION

The use of intrapartum rapid test to diagnose maternal GBS colonisation did not reduce the rates of antibiotics administered for preventing neonatal early-onset GBS infection than usual care, although with considerable uncertainty. The accuracy of the rapid test is within acceptable limits.

TRIAL REGISTRATION

ISRCTN74746075 . Prospectively registered on 16 April 2015.

Assessing standards for prevention of early onset group B streptococcal (GBS) disease in Ireland

Background:

Early onset group B streptococcal (GBS) disease can cause significant neonatal morbidity and mortality. There is currently no Irish national guideline for GBS screening, and protocols vary across maternity units. Polymerase chain reaction (PCR) testing at induction or labour onset informs triage for antibiotic prophylaxis; however, there are human and infrastructural resource requirements to enable widespread implementation.

Aim:

Our aim was to identify current standard practices for GBS prevention in Irish obstetric and neonatal services and to utilise this data to inform the need for, and potential impact of implementation of, a national guideline.

Methods:

A questionnaire on GBS screening, management and existing resources was completed by an informed staff member from each of the 19 Irish maternity units, including questions regarding timing and method of screening, antibiotic usage, and neonatal management.

Results:

One unit (5.2%) performs routine GBS screening at 35–37 weeks of gestation. Twelve units (63%) screen for GBS following spontaneous rupture of membranes (SROM) after 37 weeks, of which two (17%) perform PCR and ten (83%) culture testing. Seventeen units (89.3%) have access to a GeneXpert PCR machine, and of these, two (11.7%) use the machine for rapid GBS testing. Two units screen patients for GBS at either the start of labour or induction of labour. Four units (21%) use the neonatal early onset sepsis (EOS) calculator. Sixteen units (84%) do not treat asymptomatic infants born to GBS-positive mothers.

 Conclusion:

There is a lack of consistency in the methods for GBS screening and disease prevention across the country, highlighting the need for a national guideline accompanied by an implementation plan and budget to standardise care.

Molecular Characterization of Streptococcus agalactiae Isolates from Pregnant Women in Kathmandu City

Introduction

Group B streptococci (GBS) are globally recognized as one of the leading causes of neonatal sepsis and meningitis and is also known to cause adverse pregnancy outcomes such as stillbirths and miscarriages. Thus, detailed investigation of GBS in pregnant women has special significance in public health related researches.

Objectives

The present study is aimed at evaluating the prevalence of GBS colonization among pregnant women in Kathmandu city.

Methods

The study was carried out among 125 pregnant women at their trimester (35-37 weeks) (during the time period between January and June in 2018). The prevalence was determined by the culture method in HiCrome Strep B Selective Agar Base and then by using the PCR technique. The serotypes were evaluated by multiplex PCR analysis, while the antibiotics susceptibility tests were performed using the disk diffusion method.

Results

Among 125 samples studied, GBS were recorded in 24 samples (implying a prevalence of 19.2%). Furthermore, using the multiplex PCR, among 24 GBS-positive samples, 13 (54.17%) were found to be typeable while 11 (45.83%) were nontypeable. The most abundant serotype recorded in this study was type III (33.33) while the serotypes IV, V, VI, VII, and VIII were not found.

Conclusion

The isolates were sensitive towards some antibiotics such as linezolid and ceftriaxone 100%, whereas penicillin 50% and vancomycin 75% but were resistant to tetracycline and ertapenem. Serotype III was found to be predominant in the samples collected during the study period. The observed prevalence was significantly associated with the gestational period, whereas no relationship was found for other risk factors.

Modelling the effect of the introduction of antenatal screening for group B Streptococcus (GBS) carriage in the UK

OBJECTIVES

To estimate the potential impact of the addition of culture-based screening for group B streptococcus (GBS) carriage in pregnancy to a risk-based prevention policy in the UK. We aimed to establish agreement within a multidisciplinary group of key stakeholders on the model input parameters.

DESIGN

Deterministic model using a consensus approach for the selection of input parameters.

SETTING AND PARTICIPANTS

A theoretical annual cohort of 711 999 live births in the UK (excluding births by elective caesarean section).

INTERVENTIONS

Culture-based screening for GBS at 35-37 weeks of pregnancy added to the recommended risk-based prevention policy in place on the date of modelling.

OUTCOME MEASURES

Outcomes assessed included use of intrapartum antibiotic prophylaxis (IAP), early onset GBS (EOGBS), EOGBS mortality, severe EOGBS-related morbidity and maternal penicillin anaphylaxis.

RESULTS

With no prophylaxis strategy, the model estimated that there would be 421 cases of culture positive EOGBS in a year (0.59/1000 live births). In the risk-based prophylaxis scenario, 30 666 women were estimated to receive IAP and 70 cases of EOGBS were prevented. Addition of screening resulted in a further 96 260 women receiving IAP and the prevention of an additional 52 to 57 cases of EOGBS. This resulted in the prevention of three EOGBS deaths and four cases of severe disability. With screening, an additional 1675 to 1854 women receive IAP to prevent one EOGBS case and 24 065 to 32 087 receive IAP to prevent one EOGBS death.

CONCLUSIONS

The evidence base available for a broad range of model input parameters was limited, leading to uncertainty in the estimates produced by the model. Where data was limited, the model input parameters were agreed with the multidisciplinary stakeholder group, the first time this has been done to our knowledge. The main impact of screening is likely to be on the large group of low-risk women where the clinical impact of EOGBS tends to be less severe. This model suggests that the reduction in mortality and severe disability due to EOGBS with antenatal GBS screening is likely to be very limited, with a high rate of overdetection and overuse of antibiotics.

Early-onset group B streptococcal disease in a risk factor-based prevention setting: A 15-year population-based study

BACKGROUND

Intrapartum chemoprophylaxis reduces early-onset group B streptococcal disease (EOGBSD) in newborns. Some guidelines advise that intrapartum antibiotics should be offered following universal antenatal screening for GBS carriage and others recommend intrapartum antibiotics based on clinical risk factors alone. Since 1999, Queensland guidelines have recommended a risk factor-based approach. We examined trends in EOGBSD rates over time in Queensland in the setting of these guidelines and whether management of cases reflected the recommendations.

METHODS

A state-wide retrospective search of pathology databases, allowing near-complete, population-based case identification, was conducted to detect live-born infants from January 2000 to December 2014 with GBS cultured from blood or cerebrospinal fluid within seven days of age. A nested audit of EOGBSD cases comparing two epochs, 2000-2010 and 2011-2014, was performed to determine patient characteristics and guideline adherence for each case.

RESULTS

Mean incidence of EOGBSD in Queensland from 2000 to 2014 was 0.33 per 1000 live births (SD± 0.08) with no changing trend over time. The case-mortality rate in the 2011-2014 epoch was 1.2% compared to 11.9% in 2000-2004 (odds ratio (OR) 0.09, 95% confidence interval (CI) 0.002-0.67). The proportion of EOGBSD cases who were preterm infants decreased from 29.8% to 13.3% (OR 0.36, 95% CI 0.14-0.84). Of cases with risk factors in the 2011-2014 epoch, 46% received intrapartum antibiotics compared to 25% in 2000-2004 (OR 2.49, 95% CI 0.86-7.58, P = 0.09).

CONCLUSIONS

EOGBSD incidence rate in Queensland remained low during 2000-2014. However, both the 2011-2014 case-mortality rate and the proportion of preterm cases significantly decreased. Missed opportunities for intrapartum chemoprophylaxis remain.

Adverse events in women and children who have received intrapartum antibiotic prophylaxis treatment: a systematic review

Background

Adverse events from intrapartum antibiotic prophylaxis (IAP) are poorly documented yet essential to inform clinical practice for neonatal group B Streptococcus (GBS) disease prevention. In this systematic review, we appraised and synthesised the evidence on the adverse events of IAP in the mother and/or her child.

Methods

We searched MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, EMBASE, Cochrane, and Science Citation Index from date of inception until October 16th 2016. Reference lists of included studies and relevant systematic reviews were hand-searched. We included primary studies in English that reported any adverse events from intrapartum antibiotics for any prophylactic purpose compared to controls. The search was not restricted to prophylaxis for GBS but excluded women with symptoms of infection or undergoing caesarean section. Two reviewers assessed the methodological quality of studies, using the Cochrane Risk of Bias tool, and the Risk of Bias Assessment Tool for Nonrandomised Studies. Results were synthesised narratively and displayed in text and tables.

Results

From 2364 unique records, 30 studies were included. Despite a wide range of adverse events reported in 17 observational studies and 13 randomised controlled trials (RCTs), the evidence was inconsistent and at high risk of bias. Only one RCT investigated the long-term effects of IAP reporting potentially serious outcomes such as cerebral palsy; however, it had limited applicability and unclear biological plausibility. Seven observational studies showed that IAP for maternal GBS colonisation alters the infant microbiome. However, study populations were not followed through to clinical outcomes, therefore clinical significance is unknown. There was also observational evidence for increased antimicrobial resistance, however studies were at high or unclear risk of bias.

Conclusions

The evidence base to determine the frequency of adverse events from intrapartum antibiotic prophylaxis for neonatal GBS disease prevention is limited. As RCTs may not be possible, large, better quality, and longitudinal observational studies across countries with widespread IAP could fill this gap.

Trial registration

CRD42016037195.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-017-1432-3) contains supplementary material, which is available to authorized users.

Evidence synthesis to inform model-based cost-effectiveness evaluations of diagnostic tests: a methodological review of health technology assessments

BACKGROUND

Evaluations of diagnostic tests are challenging because of the indirect nature of their impact on patient outcomes. Model-based health economic evaluations of tests allow different types of evidence from various sources to be incorporated and enable cost-effectiveness estimates to be made beyond the duration of available study data. To parameterize a health-economic model fully, all the ways a test impacts on patient health must be quantified, including but not limited to diagnostic test accuracy.

METHODS

We assessed all UK NIHR HTA reports published May 2009-July 2015. Reports were included if they evaluated a diagnostic test, included a model-based health economic evaluation and included a systematic review and meta-analysis of test accuracy. From each eligible report we extracted information on the following topics: 1) what evidence aside from test accuracy was searched for and synthesised, 2) which methods were used to synthesise test accuracy evidence and how did the results inform the economic model, 3) how/whether threshold effects were explored, 4) how the potential dependency between multiple tests in a pathway was accounted for, and 5) for evaluations of tests targeted at the primary care setting, how evidence from differing healthcare settings was incorporated.

RESULTS

The bivariate or HSROC model was implemented in 20/22 reports that met all inclusion criteria. Test accuracy data for health economic modelling was obtained from meta-analyses completely in four reports, partially in fourteen reports and not at all in four reports. Only 2/7 reports that used a quantitative test gave clear threshold recommendations. All 22 reports explored the effect of uncertainty in accuracy parameters but most of those that used multiple tests did not allow for dependence between test results. 7/22 tests were potentially suitable for primary care but the majority found limited evidence on test accuracy in primary care settings.

CONCLUSIONS

The uptake of appropriate meta-analysis methods for synthesising evidence on diagnostic test accuracy in UK NIHR HTAs has improved in recent years. Future research should focus on other evidence requirements for cost-effectiveness assessment, threshold effects for quantitative tests and the impact of multiple diagnostic tests.

Accuracy of a rapid intrapartum group B Streptococcus test: A new immunochromatographic assay

OBJECTIVES

To decrease the incidence of early-onset group B streptococcal (GBS) disease, a culture-based screening of all pregnant women at 35-37 weeks is recommended. This gold standard test requires 24-72hours culture. This delay precludes its use for intrapartum screening. This study assesses a new immunoassay, the DIMA test, for identifying GBS-positive patients in the labor ward.

MATERIALS AND METHODS

This was a prospective observational study of 195 pregnant women presenting with full-term labor at a single site in France between June and August 2012. We assessed the diagnostic accuracy of intrapartum DIMA testing as compared to intrapartum GBS culture and prenatal screening at 35-38 weeks.

RESULTS

The DIMA test sensitivity and specificity were 57.1% and 83.2%, respectively, as compared to 42.9% and 97% for prenatal culture screening.

CONCLUSION

The DIMA test assay is a rapid and inexpensive test for the detection of maternal GBS colonization in the labor ward. Its sensitivity is higher than antepartum culture but its specificity is lower. Its performance was inferior to that reported for rapid polymerase chain reaction assays.

Development of a Novel Test for Simultaneous Bacterial Identification and Antibiotic Susceptibility

Background. Elucidation of a pathogen's antimicrobial susceptibility requires subculture after the organism is first isolated. This takes several days, requiring patients to be treated with broad-spectrum antibiotics. This approach contributes to the development of bacterial resistance. Methods. Microtiter wells were coated with a polyclonal antibody targeting the pathogen of interest. Bacterial suspensions were added in the presence/absence of selected antibiotics. After washing, captured bacteria were detected. Findings. Group B streptococcus (GBS), Enterococcus faecalis, and Neisseria gonorrhoeae were each detected at 105 bacteria/mL following a 20-minute incubation period. Susceptibility to select antibiotics was discernable following a 6-hour incubation period (GBS and Enterococcus). Sensitivity was increased to 10-2 bacteria/mL for GBS, 10-1 bacteria/mL for E. faecalis, and 101 bacteria/mL for N. gonorrhoeae following 18-24-hour culture. Conclusion. This novel assay allows for the highly sensitive and specific identification of a pathogen and simultaneous determination of its antimicrobial susceptibility in a reduced time.

Bladder ultrasonography for diagnosing detrusor overactivity: test accuracy study and economic evaluation

BACKGROUND

Urodynamics (UDS) has been considered the gold standard test for detrusor overactivity (DO) in women with an overactive bladder (OAB). Bladder ultrasonography to measure bladder wall thickness (BWT) is less invasive and has been proposed as an alternative test.

OBJECTIVES

To estimate the reliability, reproducibility, accuracy and acceptability of BWT in women with OAB, measured by ultrasonography, in the diagnosis of DO; to explore the role of UDS and its impact on treatment outcomes; and to conduct an economic evaluation of alternative care pathways.

DESIGN

A cross-sectional test accuracy study.

SETTING

22 UK hospitals.

PARTICIPANTS

687 women with OAB.

METHODS

BWT was measured using transvaginal ultrasonography, and DO was assessed using UDS, which was performed blind to ultrasonographic findings. Intraobserver and interobserver reproducibility were assessed by repeated measurements from scans in 37 and 57 women, respectively, and by repeated scans in 27 women. Sensitivity and specificity were computed at pre-specified thresholds. The smallest real differences detectable of BWT were estimated using one-way analysis of variance. The pain and acceptability of both tests were evaluated by a questionnaire. Patient symptoms were measured before testing and after 6 and 12 months using the International Consultation on Incontinence modular Questionnaire Overactive Bladder (short form) (ICIQ-OAB) questionnaire and a global impression of improvement elicited at 12 months. Interventions and patient outcomes were analysed according to urodynamic diagnoses and BWT measurements. A decision-analytic model compared the cost-effectiveness of care strategies using UDS, ultrasonography or clinical history, estimating the cost per woman successfully treated and the cost per quality-adjusted life-year (QALY).

RESULTS

BWT showed very low sensitivity and specificity at all pre-specified cut-off points, and there was no evidence of discrimination at any threshold (p = 0.25). Extensive sensitivity and subgroup analyses did not alter the interpretation of these findings. The smallest detectable difference in BWT was estimated to be 2 mm. Pain levels following both tests appeared relatively low. The proportion of women who found the test 'totally acceptable' was significantly higher with ultrasonography than UDS (81% vs. 56%; p < 0.001). Overall, subsequent treatment was highly associated with urodynamic diagnosis (p < 0.0001). There was no evidence that BWT had any relationship with the global impression of improvement responses at 20 months (p = 0.4). Bladder ultrasonography was more costly and less effective than the other strategies. The incremental cost-effectiveness ratio (ICER) of basing treatment on the primary clinical presentation compared with UDS was £491,500 per woman successfully treated and £60,200 per QALY. Performing a UDS in those women with a clinical history of mixed urinary incontinence had an ICER of £19,500 per woman successfully treated and £12,700 per QALY compared with the provision of urodynamic to all women. For DO cases detected, UDS was the most cost-effective strategy.

CONCLUSION

There was no evidence that BWT had any relationship with DO, regardless of the cut-off point, nor any relationship to symptoms as measured by the ICIQ-OAB. Bladder ultrasonography has no diagnostic or prognostic value as a test in this condition. Furthermore, despite its greater acceptability, BWT measurement was not sufficiently reliable or reproducible.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN46820623.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 7. See the NIHR Journals Library website for further project information.

Isothermal Recombinase Polymerase Amplification Assay Applied to the Detection of Group B Streptococci in Vaginal/Anal Samples

BACKGROUND

Group B streptococcal infections are the leading cause of sepsis and meningitis in newborns. A rapid and reliable method for the detection of this pathogen at the time of delivery is needed for the early treatment of neonates. Isothermal amplification techniques such as recombinase polymerase amplification have advantages relative to PCR in terms of the speed of reaction and simplicity.

METHODS

We studied the clinical performance of recombinase polymerase amplification for the screening of group B streptococci in vaginal/anal samples from 50 pregnant women. We also compared the limit of detection and the analytical specificity of this isothermal assay to real-time PCR (RT-PCR).

RESULTS

Compared to RT-PCR, the recombinase polymerase amplification assay showed a clinical sensitivity of 96% and a clinical specificity of 100%. The limit of detection was 98 genome copies and the analytical specificity was 100% for a panel of 15 bacterial and/or fungal strains naturally found in the vaginal/anal flora. Time-to-result for the recombinase polymerase amplification assay was &lt;20 min compared to 45 min for the RT-PCR assay; a positive sample could be detected as early as 8 min.

CONCLUSIONS

We demonstrate the potential of isothermal recombinase polymerase amplification assay as a clinically useful molecular diagnostic tool that is simple and faster than PCR/RT-PCR. Recombinase polymerase amplification offers great potential for nucleic acid–based diagnostics at the point of care.

Bladder pain syndrome: validation of simple tests for diagnosis in women with chronic pelvic pain: BRaVADO study protocol

Background

Bladder pain syndrome (BPS), a condition with no gold standard diagnosis, comprises of a cluster of signs and symptoms. Bladder filling pain and bladder wall tenderness are two basic clinical features, present in a high number of sufferers. This study will validate the performance of these simple tests for BPS in women with chronic pelvic pain (CPP).

Methods/design

We will conduct a prospective test validation study amongst women with unexplained CPP presenting to gynaecology outpatient clinics. Two index tests will be performed: patient reported bladder filling pain and bladder wall tenderness on internal pelvic bimanual examination. A final diagnosis of BPS will be made by expert consensus panel. We will assess the rates of index tests in women with CPP; evaluate the correlation between index tests and Pelvic Pain Urgency/ Frequency (PUF) questionnaire results; and determine index test sensitivity and specificity using a range of analytical methods. Assuming a 50% prevalence of BPS and an 80% power approximately 152 subjects will be required exclude sensitivity of < 55% at 70% sensitivity.

Discussion

The results of this test validation study will be used to identify whether a certain combination of signs and symptoms can accurately diagnose BPS.

Trial registration

ISRCTN13028601

Feasibility of using microbiology diagnostic tests of moderate or high complexity at the point - of - care in a delivery suite

Point-of-care testing (POCT) is one of the fastest growing sectors of laboratory diagnostics. Most tests in routine use are haematology or biochemistry tests that are of low complexity. Microbiology POCT has been constrained by a lack of tests that are both accurate and of low complexity. We describe our experience of the practical issues around using more complex POCT for detection of Group B streptococci (GBS) in swabs from labouring women. We evaluated two tests for their feasibility in POCT: an optical immune assay (Biostar OIA Strep B, Inverness Medical, Princetown, NJ) and a PCR (IDI-Strep B, Cepheid, Sunnyvale, CA), which have been categorised as being of moderate and high complexity, respectively. A total of 12 unqualified midwifery assistants (MA) were trained to undertake testing on the delivery suite. A systematic approach to the introduction and management of POC testing was used. Modelling showed that the probability of test results being available within a clinically useful timescale was high. However, in the clinical setting, we found it impossible to maintain reliable availability of trained testers. Implementation of more complex POC testing is technically feasible, but it is expensive, and may be difficult to achieve in a busy delivery suite.

Optimization of a rapid diagnostic test for detection of group B streptococcus from antepartum patients

We analyzed the performance of a new rapid diagnostic test for use in determining group B streptococcus colonization in pregnancy. Vaginal-rectal specimens were compared by the rapid test, a commercial laboratory culture result, and an in-house culture. Of 150 patient samples, 72 were positive by the rapid test, giving a prevalence of 48.0% versus 24.7% by traditional culture. Characterization of these results showed cross-reactivity with Enterococcus. The addition of bacitracin reduced this interference, and when reanalyzed, a colonization rate of 31.3% was found (P = 0.3961, chi-square), as well as a sensitivity of 100% (95% confidence interval [CI] 89.1-100) and a specificity of 93.6% (95% CI 86.9-97.2). The addition of bacitracin greatly improves the reliability of this diagnostic test and demonstrates a novel approach to reduce interference. An accurate determination of the test's sensitivity and specificity, however, awaits enrollment of the remaining subjects.

Epidemiology of group B Streptococcus ST-17 clone in pregnant women of South Taiwan

OBJECTIVES

We aimed to utilize a simple molecular assay to simultaneously detect both group B Streptococcus (GBS) and virulent ST-17 rectovaginal colonization. We also attempted to estimate the prevalence of maternal GBS and ST-17 carriers and to evaluate their seasonal association.

SUBJECTS AND METHODS

We used an optimized multiplex PCR method employing scp-B and ST-17 primers to analyze DNA extracted from rectovaginal swabs of 3,064 cases collected over 3 years. The incidence trends, seasonal variations, and temperature preference were analyzed.

RESULTS

The overall prevalence of maternal colonization for GBS and ST-17 clone were 13.25 and 2.48%, respectively. The ST-17 to GBS ratio was 18.72%. The occurrence of ST-17 colonization was significantly associated with seasonal variations with a preference for lower temperatures.

CONCLUSIONS

We developed a novel multiplex PCR method suitable for the simultaneous detection of GBS and ST-17 clone. The phenomenon of lower temperature preference for ST-17 clone necessitates further investigation. The epidemiological data for GBS and ST-17 incidence are especially important to establish a public policy for universal GBS screening in the future.

How can the microbiologist help in diagnosing neonatal sepsis?

Neonatal sepsis can be classified into two subtypes depending upon whether the onset of symptoms is before 72 hours of life (early-onset neonatal sepsis—EONS) or later (late-onset neonatal sepsis—LONS). These definitions have contributed greatly to diagnosis and treatment by identifying which microorganisms are likely to be responsible for sepsis during these periods and the expected outcomes of infection. This paper focuses on the tools that microbiologist can offer to diagnose and eventually prevent neonatal sepsis. Here, we discuss the advantages and limitation of the blood culture, the actual gold standard for sepsis diagnosis. In addition, we examine the utility of molecular techniques in the diagnosis and management of neonatal sepsis.

Myth: Group B streptococcal infection in pregnancy: comprehended and conquered

Group B streptococcus (GBS) is a common inhabitant of the bowel, and frequently colonises the vagina. It rarely causes disease, except in neonates, where it is the most common cause of serious neonatal infection. Although GBS can be transmitted sexually, it is common even in adults who have never been sexually active and is not a sexually transmitted disease. Currently, the most widely used effective method for detecting colonisation is taking a low vaginal and rectal swab and culturing GBS using enriched media culture. GBS cannot reliably be eradicated by antibiotic treatment but intravenous penicillin given to the mother during labour can prevent up to 90% of early onset GBS disease. Screening and antibiotic prophylaxis has resulted in an 80% fall in early onset disease in the USA, and has been successfully implemented in many countries. There is no systematic screening in the UK, where the incidence continues to rise.

Real-time PCR assay provides reliable assessment of intrapartum carriage of group B Streptococcus

The objective of this study was to determine the reliability of the real-time PCR assay for determining the group B Streptococcus (GBS) status of women in labor. In this prospective study we compared the results of culture and PCR testing of vaginal and rectal samples collected by nursing staff when women were in labor. Patients' charts were also reviewed to obtain relevant information about pregnancy risk factors. Our results demonstrated a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 90.5%, 96.1%, 86.4%, and 97.4%, respectively, for rapid PCR. Of the 196 women evaluated, 29 (14.8%) presented with unknown GBS status, 11 (37.9%) of whom received unnecessary intrapartum antibiotics. The rapid real-time PCR test was robust and was able to reliably detect the presence of GBS in women in labor within 1 h of specimen submission to the laboratory. We recommend that the rapid PCR test be targeted to women who present in labor with unknown GBS status. In cases where the laboratory does not offer 24-h availability of testing, sample collection followed by PCR testing the next morning is still valuable and provides reliable results 24 to 48 h faster than culture and will aid appropriate decision-making regarding continuing or stopping antibiotics for neonates of women with unknown GBS status.