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

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.

High prevalence of Group B Streptococcus colonization among pregnant women in Amman, Jordan

Background

Little is known of the burden of Group B Streptococcus (GBS) colonization among pregnant women in Jordan. We conducted a pilot study to determine the prevalence of GBS among pregnant women in Amman, Jordan, where GBS testing is not routine. We also explored GBS serotypes and the performance of a rapid GBS antigen diagnostic test.

Methods

We collected vaginal-rectal swabs from women who presented for labor and delivery at Al-Bashir Hospital. Three methods were used to identify GBS: Strep B Rapid Test (Creative Diagnostics), blood agar media (Remel) with confirmed with BBL Streptocard acid latex test (Becton Dickinson), and CHROMagar StrepB (Remel). Results were read by a senior microbiologist. We defined our gold standard for GBS-positive as a positive blood agar culture confirmed by latex agglutination and positive CHROMagar. PCR testing determined serotype information. Demographic and clinical data were also collected.

Results

In April and May 2015, 200 women were enrolled with a median age of 27 years (IQR: 23–32); 89.0% were Jordanian nationals and 71.9% completed secondary school. Median gestational age was 38 weeks (IQR: 37–40); most women reported prenatal care (median 9 visits; IQR: 8–12). Median parity was 2 births (IQR: 1–3). Pre-pregnancy median BMI was 24.1 (IQR: 21.5–28.0) and 14.5% reported an underlying medical condition. Obstetric complications included gestational hypertension (9.5%), gestational diabetes (6.0%), and UTI (53.5%), of which 84.5% reported treatment. Overall, 39 (19.5%) of women were GBS-positive on blood agar media and CHROMagar, while 67 (33.5%) were positive by rapid test (36% sensitivity, 67% specificity). Serotype information was available for 25 (64%) isolates: III (48%), Ia (24%), II (20%), and V (8%). No demographic or clinical differences were noted between GBS+ and GBS-negative women.

Conclusions

Nearly one in five women presenting for labor in Jordan was colonized with GBS, with serotype group III as the most common. The rapid GBS antigen diagnostic had low sensitivity and specificity. These results support expanded research in the region, including defining GBS resistance patterns, serotyping information, and risk factors. It also emphasizes the need for routine GBS testing and improved rapid GBS diagnostics for developing world settings.

Point-of-care (POC) diagnosis of bacterial vaginosis (BV) using VGTest™ ion mobility spectrometry (IMS) in a routine ambulatory care gynecology clinic

PURPOSE

A new CE-marked portable desktop ion mobility spectrometer (VGTest) was used for detection of malodorous biogenic amines indicative of bacterial vaginosis (BV). This study aimed to assess the performance of this testing method for the first time in a routine ambulatory care clinic and to determine the relative levels of biogenic amines in vaginal fluid of BV.

METHODS

Vaginal and cervical swabs (n = 57) were surveyed for infections. Cases of BV (n = 18) confirmed positive according to "Amsel" criteria and normal controls (n = 39) showing no infection under clinical examination and testing negative in wet mount microscopy were included in the IMS analysis.

RESULTS

The trimethylamine (TMA) content in vaginal fluid of the BV-positive cases, AUCTMA/AUCTotal [mean 0.215 (range 0.15-0.35)] was significantly higher than normal controls [mean 0.06 (range 0.048-0.07)] p < 0.0001. The putrescine (1,4-diaminobutane, PUT) and cadaverine (1,5-diaminopentane, CAD) of BV-positive cases were above controls at borderline significance. The AUCTMA/AUCTotal ratios correlated neither with AUCPUT/AUCTotal nor AUCCAD/AUCTotal among BV-positive patients. In contrast, among normal controls all the biogenic amines were at a low level and the linear regression analysis revealed striking positive correlations of AUCTMA/AUCTotal with AUCPUT/AUCTotal (p < 0.05) and AUCCAD/AUCTotal (p < 0.001). The test shows 83 % sensitivity and 92 % specificity at a cut-off of AUCTMA/AUCTotal = 0.112 and AUC of receiver operator characteristic = 0.915 (0.81-0.97, 95 % CI).

CONCLUSIONS

VGTest-IMS is accurate and feasible for point-of-care testing of BV in the ambulatory care setting. Further evaluations are in progress to assess the utility of VGTest-IMS for differential diagnosis of candidosis, non-BV infection and common inflammatory conditions.

Point-of-Care Testing for Clostridium Difficile Infection: A Real-World Feasibility Study of a Rapid Molecular Test in Two Hospital Settings

Introduction

In the developed world, Clostridium difficile infection (CDI) is the most important cause of nosocomial infectious diarrhea. In addition to providing epidemiological data and helping to indicate that a local outbreak may be occurring, laboratory tests are used to augment clinical decisions on individual patients. Very rarely do diagnostic tests provide results at the point of decision making; in the intervening period between requesting investigations on a patient with suspected CDI and return of the laboratory result, decisions must be made regarding patient isolation and treatment.

Methods

A 22-month, real-world feasibility study was conducted in patients with clinically significant diarrhea, in a London Hospital between March 2011 and January 2013, in three older persons’ wards and two intensive care units (ICUs) to determine acceptability, ease of use, change in turnaround time and clinical utility of a rapid, polymerase chain reaction (PCR)-based point-of-care test (POCT) (Cepheid GeneXpert^®, Sunnyvale, California, USA) for diagnosis of Clostridium difficile. Nurses in the older persons’ ward and laboratory technicians in the ICU were trained to perform the test. Residual samples were sent to the centralized laboratory for parallel testing using a two-step algorithm.

Results

A total of 335 samples were tested using the POCT with a median turnaround time of 1.85 h compared with 18 h for the centralized laboratory test. Overall agreement with centralized laboratory testing was 98.1%. Discrepant samples were more frequent on elderly wards than ICU. Overall 20/335 (6%) processing errors were encountered and were highest in the first few months of the study. Significantly more processing errors occurred on the older persons’ wards 13/102 (12.7%) than on ICU 7/271 (2.6%). Older persons’ patients who had POCT were significantly less likely to have a test requested for bacterial stool culture (3.1% vs. 10.9% p = 0.044). This difference was not observed in the ICU patients. No other differences in ancillary test requesting, mortality or length of stay were observed.

Conclusions

The majority of users reported that the POCT was easy to perform and was an acceptable part of their job. POCT using this system is feasible and acceptable to nursing staff and technicians working within these two hospital-based settings.

Electronic supplementary material

The online version of this article (doi:10.1007/s40121-014-0038-6) contains supplementary material, which is available to authorized users.

Molecular-based screening for perinatal group B streptococcal infection: implications for prevention and therapy

Group B streptococci (GBS) are a leading cause of infectious neonatal morbidity and mortality. Timely and accurate identification of colonized pregnant women is imperative to implement intrapartum antibioprophylaxis (IAP) to reduce the risk of early neonatal sepsis. Current guidelines recommend screening for GBS carriage with vaginal-rectal cultures. However, cultures require 24-72 h, thus precluding their use for intrapartum screening and these are only performed at 35-37 weeks gestation. New rapid molecular-based tests can detect GBS within hours. They have the potential to be used intrapartum and to allow for selective IAP in women carrying GBS. An advantage is that they can sometimes be performed by non-laboratory staff in the labor suite, thus avoiding delays in sample transfers to the microbiology laboratory. Another possible use of molecular-based assays is for the diagnosis of neonatal sepsis, where tests with a short turnaround time and high sensitivity and specificity are crucial. In this situation, the detection of microorganisms once antibiotic therapy has already been started is important, as treatment is started immediately once sepsis is suspected without waiting for microbiological confirmation. In this article, we discuss the state-of-the-art molecular-based tests available for GBS screening during pregnancy, as well as their implications for IAP for the diagnosis and prevention of neonatal sepsis.

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.