Search strategy and evidence selection

Search strategy and evidence selection

Search strategy

The search strategy was designed to identify evidence on the clinical and cost effectiveness of the Xpert GBS assay for direct intrapartum screening in labour or delivery.

The strategy was developed for MEDLINE (Ovid interface). The strategy was devised using a combination of subject indexing terms and free text search terms in the title, abstract and keyword heading word fields. The search terms were identified through discussion within the research team, scanning background literature, browsing database thesauri and use of the PubMed PubReminer tool. The strategy reflected the nature of the Medtech innovation briefing assessments as rapid evidence reviews.

The search comprised 3 concepts:

1) setting (pregnancy / labour / neonatal health);

2) group B streptococcus;

3) polymerase chain reaction.

Additional search lines on brand name, and manufacturer name combined with GBS terms, were also used. These lines were designed to capture any records that may have been missed by the 3 concept approach.

The strategy excluded non‑English language publications. Animal studies were also excluded using a standard algorithm. No additional filters for study design were applied. The results were limited to studies added to the database from 2005 to January 2015, this reflected the date when the device was introduced (2006).

The final MEDLINE strategy was peer‑reviewed by an independent information specialist. The MEDLINE strategy was translated appropriately for the other databases searched. The PubMed search was limited to records that were not fully indexed on MEDLINE.

The following databases were searched:

  • Cochrane Central Register of Controlled Trials (Cochrane Library, Wiley)

  • Cochrane Database of Systematic Reviews (Cochrane Library, Wiley)

  • Database of Abstracts of Reviews of Effects (Cochrane Library, Wiley)

  • Embase (Ovid SP)

  • Health Technology Assessment Database (Cochrane Library, Wiley)

  • MEDLINE and MEDLINE in Process (Ovid SP)

  • NHS Economic Evaluation Database (Cochrane Library, Wiley)

  • PubMed

Evidence selection

A total of 419 records were retrieved from the literature search. After de‑duplication, 265 records remained and were sifted against the inclusion criteria at title and abstract level.

Records were sifted independently by 2 researchers. Any disagreements were discussed and agreement was reached in all cases, so a third independent arbiter was not required. The first sift removed 237 records based on the following exclusion criteria:

  • articles of poor relevance against search terms

  • publication types that were out of scope

  • non‑English language studies

  • conference abstracts

  • review articles.

Full articles were retrieved for 28 of the remaining studies. Full text assessment was done independently by 2 researchers to identify relevant primary research addressing the key outcomes of interest. At this stage, 18 papers were excluded:

  • studies on different commercial or experimental systems: 10

  • letters to editors: 4

  • same study in a different journal: 1

  • incorrect setting (not at point of care): 1

  • cost‑effectiveness studies: 2.

Ten studies remained, which included 1 randomised controlled trial and 9 diagnostic accuracy studies that included a reference standard. Two diagnostic accuracy studies were further excluded because they did not include a suitable reference standard. Six diagnostic accuracy studies were summarised briefly but excluded from the full evidence review because they did not include primary evidence investigating the feasibility of implementing intrapartum antibiotics based on the results of the intrapartum Xpert GBS test. The randomised controlled trial and the diagnostic accuracy study that assessed the feasibility of intrapartum antibiotic prophylaxis based on Xpert GBS results became the focus of the evidence review.