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

OBJECTIVE: To determine the accuracy, acceptability and cost-effectiveness of polymerase chain reaction (PCR) and optical immunoassay (OIA) rapid tests for maternal group B streptococcal (GBS) colonisation at labour. DESIGN: A test accuracy study was used to determine the accuracy of rapid tests for GBS colonisation of women in labour. Acceptability of testing to participants was evaluated through a questionnaire administered after delivery, and acceptability to staff through focus groups. A decision-analytic model was constructed to assess the cost-effectiveness of various screening strategies. SETTING: Two large obstetric units in the UK. PARTICIPANTS: Women booked for delivery at the participating units other than those electing for a Caesarean delivery. INTERVENTIONS: Vaginal and rectal swabs were obtained at the onset of labour and the results of vaginal and rectal PCR and OIA (index) tests were compared with the reference standard of enriched culture of combined vaginal and rectal swabs. MAIN OUTCOME MEASURES: The accuracy of the index tests, the relative accuracies of tests on vaginal and rectal swabs and whether test accuracy varied according to the presence or absence of maternal risk factors. RESULTS: PCR was significantly more accurate than OIA for the detection of maternal GBS colonisation. Combined vaginal or rectal swab index tests were more sensitive than either test considered individually [combined swab sensitivity for PCR 84% (95% CI 79-88%); vaginal swab 58% (52-64%); rectal swab 71% (66-76%)]. The highest sensitivity for PCR came at the cost of lower specificity [combined specificity 87% (95% CI 85-89%); vaginal swab 92% (90-94%); rectal swab 92% (90-93%)]. The sensitivity and specificity of rapid tests varied according to the presence or absence of maternal risk factors, but not consistently. PCR results were determinants of neonatal GBS colonisation, but maternal risk factors were not. Overall levels of acceptability for rapid testing amongst participants were high. Vaginal swabs were more acceptable than rectal swabs. South Asian women were least likely to have participated in the study and were less happy with the sampling procedure and with the prospect of rapid testing as part of routine care. Midwives were generally positive towards rapid testing but had concerns that it might lead to overtreatment and unnecessary interference in births. Modelling analysis revealed that the most cost-effective strategy was to provide routine intravenous antibiotic prophylaxis (IAP) to all women without screening. Removing this strategy, which is unlikely to be acceptable to most women and midwives, resulted in screening, based on a culture test at 35-37 weeks' gestation, with the provision of antibiotics to all women who screened positive being most cost-effective, assuming that all women in premature labour would receive IAP. The results were sensitive to very small increases in costs and changes in other assumptions. Screening using a rapid test was not cost-effective based on its current sensitivity, specificity and cost. CONCLUSIONS: Neither rapid test was sufficiently accurate to recommend it for routine use in clinical practice. IAP directed by screening with enriched culture at 35-37 weeks' gestation is likely to be the most acceptable cost-effective strategy, although it is premature to suggest the implementation of this strategy at present.

Intrapartum tests for group B streptococcus:accuracy and acceptability of screening

Objective: To assess the accuracy and acceptability of polymerase chain reaction (PCR) and optical immunoassay (OIA) tests for the detection of maternal group B streptococcus (GBS) colonisation during labour, comparing their performance with the current UK policy of risk factor-based screening. Design Diagnostic test accuracy study. Setting and population Fourteen hundred women in labour at two large UK maternity units provided vaginal and rectal swabs for testing. Methods The PCR and OIA index tests were compared with the reference standard of selective enriched culture, assessed blind to index tests. Factors influencing neonatal GBS colonisation were assessed using multiple logistic regression, adjusting for antibiotic use. The acceptability of testing to participants was evaluated through a structured questionnaire administered after delivery. Main outcome measures The sensitivity and specificity of PCR, OIA and risk factor-based screening. Results Maternal GBS colonisation was 21% (19-24%) by combined vaginal and rectal swab enriched culture. PCR test of either vaginal or rectal swabs was more sensitive (84% [79-88%] versus 72% [65-77%]) and specific (87% [85-89%] versus 57% [53-60%]) than OIA (P <0.001), and far more sensitive (84 versus 30% [25-35%]) and specific (87 versus 80% [77-82%]) than risk factor-based screening (P <0.001). Maternal antibiotics (odds ratio, 0.22 [0.07-0.62]; P = 0.004) and a positive PCR test (odds ratio, 29.4 [15.8-54.8]; P <0.001) were strongly related to neonatal GBS colonisation, whereas risk factors were not (odds ratio, 1.44 [0.80-2.62]; P = 0.2). Conclusion Intrapartum PCR screening is a more accurate predictor of maternal and neonatal GBS colonisation than is OIA or risk factor-based screening, and is acceptable to women. © RCOG 2010 BJOG An International Journal of Obstetrics and Gynaecology.

Progesterone release from a silicone intravaginal ring in pigtailed macaques

Background: Heterosexual HIV transmission continues to spread worldwide. Intravaginal rings (IVRs) formulated with antiretroviral drugs hold great promise for HIV prevention in women. IVRs provide the benefit of being coitally-independent and coitally-covert for an extended period. As a proof-of-concept, we tested the in vivo release of progesterone from a silicone elastomer vaginal ring device. Methods: Six female pig-tailed macaques were treated with a GnRH agonist (Lupron) prior to ring placement. Four macaques received a progesterone-loaded silicone ring, and two macaques received a blank silicone ring. Blood, vaginal swabs, CVL, and/or biopsies were collected during ring placement, and after ring removal. Results: The median plasma progesterone levels for macaques with a progesterone IVR were 13,973 pg/ml (day 3), 12,342 pg/ml (day 7), 10,112 pg/ml (day 14), 8445 pg/ml (day 21) and 8061 pg/ml (day 28), with a significant decrease from day 14 to day 21 (P = 0.0286). The median plasma progesterone levels for macaques with a blank IVR were 221±±± ±±88 pg/ml. Macaques with a progesterone IVR had CVL progesterone levels of 20,935 pg/ml (day 7), 6892 pg/ml (day 21) and 11,515 pg/ml (day 28). Macaques with a blank IVR had CVL progesterone levels of 29 �± 13 pg/ml. There were no disturbances to the normal vaginal microflora, and plasma and CVL cytokine analysis did not indicate a proinflammatory response due to ring placement. The vaginal biopsies did not display any pathology following ring removal. Overall, the IVRs were well tolerated without any indication of inflammation or significant changes in the vaginal compartment.

Perceptions of self-testing for chlamydia:understanding and predicting self-test use

Background: Self-testing technology allows people to test themselves for chlamydia without professional support. This may result in reassurance and wider access to chlamydia testing, but anxiety could occur on receipt of positive results. This study aimed to identify factors important in understanding self-testing for chlamydia outside formal screening contexts, to explore the potential impacts of self-testing on individuals, and to identify theoretical constructs to form a Framework for future research and intervention development. Methods: Eighteen university students participated in semi-structured interviews; eleven had self-tested for chlamydia. Data were analysed thematically using a Framework approach. Results: Perceived benefits of self-testing included its being convenient, anonymous and not requiring physical examination. There was concern about test accuracy and some participants lacked confidence in using vulvo-vaginal swabs. While some participants expressed concern about the absence of professional support, all said they would seek help on receiving a positive result. Factors identified in Protection Motivation Theory and the Theory of Planned Behaviour, such as response efficacy and self-efficacy, were found to be highly salient to participants in thinking about self-testing. Conclusions: These exploratory findings suggest that self-testing independently of formal health care systems may no more negatively impact people than being tested by health care professionals. Participants’ perceptions about self-testing behaviour were consistent with psychological theories. Findings suggest that interventions which increase confidence in using self-tests and that provide reassurance of test accuracy may increase self-test intentions.